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  <xsd:element id="csgp_BusinessAcquisitionEquityInterestIssuedOrIssuableAmountPerShare" name="BusinessAcquisitionEquityInterestIssuedOrIssuableAmountPerShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
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  <xsd:element id="csgp_BusinessAcquisitionPurchasePriceAllocationAcquiredCustomerBase" name="BusinessAcquisitionPurchasePriceAllocationAcquiredCustomerBase" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="csgp_BusinessAcquisitionPurchasePriceAllocationAcquiredDatabaseTechnology" name="BusinessAcquisitionPurchasePriceAllocationAcquiredDatabaseTechnology" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
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  <xsd:element id="csgp_CapitalLeasesFutureMinimumPaymentsDueYearsOneAndTwo" name="CapitalLeasesFutureMinimumPaymentsDueYearsOneAndTwo" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element id="csgp_CorporateBondsFairValueDisclosure" name="CorporateBondsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_CostarGroupInc2007StockIncentivePlanMember" name="CostarGroupInc2007StockIncentivePlanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_CumulativeEbitdaRequiredForAwardSharesToVest" name="CumulativeEbitdaRequiredForAwardSharesToVest" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
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  <xsd:element abstract="true" id="csgp_DatabaseTechnologyAndTradeNamesMember" name="DatabaseTechnologyAndTradeNamesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
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  <xsd:element id="csgp_DebtInstrumentBasisSpreadOnVariableRatePerAnnum" name="DebtInstrumentBasisSpreadOnVariableRatePerAnnum" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_DebtInstrumentTermOfLoan" name="DebtInstrumentTermOfLoan" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_DebtIssuanceLegalFees" name="DebtIssuanceLegalFees" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="csgp_DebtIssuanceUnderwritingFees" name="DebtIssuanceUnderwritingFees" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
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  <xsd:element id="csgp_DeferredTaxLiabilitiesDepreciation" name="DeferredTaxLiabilitiesDepreciation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="csgp_DeferredTaxLiabilitiesPrepaids" name="DeferredTaxLiabilitiesPrepaids" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="csgp_DefinedBenefitPlanAdministrativeExpense" name="DefinedBenefitPlanAdministrativeExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_DocumentAndEntityInformationAbstract" name="DocumentAndEntityInformationAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_EarlyTerminationAgreementBostonOfficeMember" name="EarlyTerminationAgreementBostonOfficeMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_EmployeePlansAbstract" name="EmployeePlansAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_EquityOfferingTextBlock" name="EquityOfferingTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ExcessCashFlowPaymentMaturityPeriodWithinIssuanceOfFinancialStatements" name="ExcessCashFlowPaymentMaturityPeriodWithinIssuanceOfFinancialStatements" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ExercisableAtEndOfPeriodMaximum" name="ExercisableAtEndOfPeriodMaximum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_ExercisableAtEndOfPeriodMinimum" name="ExercisableAtEndOfPeriodMinimum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_ExercisedMaximum" name="ExercisedMaximum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ExercisedMinimum" name="ExercisedMinimum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_ExternalCustomersMember" name="ExternalCustomersMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_FairValueLiabilitiesDeferredConsiderationUponAcquisition" name="FairValueLiabilitiesDeferredConsiderationUponAcquisition" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="csgp_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityAdjustments" name="FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityAdjustments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_FederalFundsRateMember" name="FederalFundsRateMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_FirstExcessCashFlowRepaymentPercentage" name="FirstExcessCashFlowRepaymentPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_FirstExcessCashFlowRepaymentRequirement" name="FirstExcessCashFlowRepaymentRequirement" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_FixedInterestRateTypeAxis" name="FixedInterestRateTypeAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_FixedInterestRateTypeDomain" name="FixedInterestRateTypeDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_FurnitureAndOfficeEquipmentMember" name="FurnitureAndOfficeEquipmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_FurnitureOfficeEquipmentAndResearchVehiclesMember" name="FurnitureOfficeEquipmentAndResearchVehiclesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_GoodwillAbstract" name="GoodwillAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_GoodwillMember" name="GoodwillMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_GrantedMaximum" name="GrantedMaximum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_GrantedMinimum" name="GrantedMinimum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_IncomeTaxReconciliationDisregardedEntityElection" name="IncomeTaxReconciliationDisregardedEntityElection" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="csgp_Increaseinsharesauthorized" name="Increaseinsharesauthorized" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_Increaseinsharesofcommonstockissuedpursuanttostockplan" name="Increaseinsharesofcommonstockissuedpursuanttostockplan" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_IntangibleAssetNetBookValue" name="IntangibleAssetNetBookValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_IntangiblesAndOtherAssetsAbstract" name="IntangiblesAndOtherAssetsAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_InternationalMember" name="InternationalMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_IntersegmentRevenueMember" name="IntersegmentRevenueMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_LandsofamericaMember" name="LandsofamericaMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_LeaseOfOfficeBuildingMember" name="LeaseOfOfficeBuildingMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_LiabilitiesDeferredConsiderationFairValueDisclosuredeferredConsideration" name="LiabilitiesDeferredConsiderationFairValueDisclosuredeferredConsideration" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="csgp_LiborMaturityPeriod" name="LiborMaturityPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_LiborMember" name="LiborMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_LoopnetMember" name="LoopnetMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_LoopnetOfficeConsolidationSanFranciscoMember" name="LoopnetOfficeConsolidationSanFranciscoMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MaximumDebtServiceCoverageRatio" name="MaximumDebtServiceCoverageRatio" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MaximumOriginalMaturityOfHighlyLiquidInvestmentsToBeConsideredCashEquivalents" name="MaximumOriginalMaturityOfHighlyLiquidInvestmentsToBeConsideredCashEquivalents" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MaximumPercentageOfEmployeeTotalCompensationMatchedByEmployer" name="MaximumPercentageOfEmployeeTotalCompensationMatchedByEmployer" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MaximumTotalLeverageRatioAfterEightFiscalQuarters" name="MaximumTotalLeverageRatioAfterEightFiscalQuarters" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MaximumTotalLeverageRatioForFifthThroughEighthQuartersAfterClosingDate" name="MaximumTotalLeverageRatioForFifthThroughEighthQuartersAfterClosingDate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MaximumTotalLeverageRatioForThirdAndFourthQuartersAfterClosingDate" name="MaximumTotalLeverageRatioForThirdAndFourthQuartersAfterClosingDate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MaximumTotalLeverageRatioForTwoQuartersAfterClosing" name="MaximumTotalLeverageRatioForTwoQuartersAfterClosing" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MinimumContractualMaturitiesOnUnderlyingSecuritiesInvolvedInAuctionRateSecurities" name="MinimumContractualMaturitiesOnUnderlyingSecuritiesInvolvedInAuctionRateSecurities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MinimumContractualMaturityForrAvailableForSaleShortTermInvestmentsToBeConsideredCurrent" name="MinimumContractualMaturityForrAvailableForSaleShortTermInvestmentsToBeConsideredCurrent" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MinimumMaturityTermAtTimeOfPurcahseToBeConsideredShortTermInvestments" name="MinimumMaturityTermAtTimeOfPurcahseToBeConsideredShortTermInvestments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_MinimumNumberOfCurrentLitigationMatters" name="MinimumNumberOfCurrentLitigationMatters" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_MoneyMarketFundsFairValueDisclosure" name="MoneyMarketFundsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_NewRevolvingCreditFacilityMember" name="NewRevolvingCreditFacilityMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_NewTermLoanMember" name="NewTermLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_NumberOfClassActionLawsuitsBroughtByAllegedLoopnetStockholders" name="NumberOfClassActionLawsuitsBroughtByAllegedLoopnetStockholders" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_NumberOfConsecutiveQuartersToMantainCumulativeEbitdaRequiredForAwardSharesToVest" name="NumberOfConsecutiveQuartersToMantainCumulativeEbitdaRequiredForAwardSharesToVest" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_NumberOfCustomersAccoutingForMoreThanFivePercentOfRevenue" name="NumberOfCustomersAccoutingForMoreThanFivePercentOfRevenue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_NumberOfDaysAfterClosingDateToPayRemainingBalance" name="NumberOfDaysAfterClosingDateToPayRemainingBalance" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_NumberOfDistinctIntangibleAsset" name="NumberOfDistinctIntangibleAsset" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable10Member" name="OptionsExercisable10Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable11Member" name="OptionsExercisable11Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable1Member" name="OptionsExercisable1Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable2Member" name="OptionsExercisable2Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable3Member" name="OptionsExercisable3Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable4Member" name="OptionsExercisable4Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable5Member" name="OptionsExercisable5Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable6Member" name="OptionsExercisable6Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable7Member" name="OptionsExercisable7Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable8Member" name="OptionsExercisable8Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisable9Member" name="OptionsExercisable9Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsExercisableAbstract" name="OptionsExercisableAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding10Member" name="OptionsOutstanding10Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding11Member" name="OptionsOutstanding11Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding1Member" name="OptionsOutstanding1Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding2Member" name="OptionsOutstanding2Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding3Member" name="OptionsOutstanding3Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding4Member" name="OptionsOutstanding4Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding5Member" name="OptionsOutstanding5Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding6Member" name="OptionsOutstanding6Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding7Member" name="OptionsOutstanding7Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding8Member" name="OptionsOutstanding8Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OptionsOutstanding9Member" name="OptionsOutstanding9Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_OtherAssetsAndLiabilitiesMember" name="OtherAssetsAndLiabilitiesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ParValueOfCompanyHeldAuctionRateSecurities" name="ParValueOfCompanyHeldAuctionRateSecurities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfCompanyMatchOfEmployeeContribution" name="PercentageOfCompanyMatchOfEmployeeContribution" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_PercentageOfLoanAmortizationInYearFive" name="PercentageOfLoanAmortizationInYearFive" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfLoanAmortizationInYearFour" name="PercentageOfLoanAmortizationInYearFour" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfLoanAmortizationInYearOne" name="PercentageOfLoanAmortizationInYearOne" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfLoanAmortizationInYearThree" name="PercentageOfLoanAmortizationInYearThree" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfLoanAmortizationInYearTwo" name="PercentageOfLoanAmortizationInYearTwo" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfPurchasePriceHeldInEscrow" name="PercentageOfPurchasePriceHeldInEscrow" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfPurchasePriceOfCompanysCommonStockToMarketPrice" name="PercentageOfPurchasePriceOfCompanysCommonStockToMarketPrice" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_PercentageOfPurchasePricePaidOnClosingDate" name="PercentageOfPurchasePricePaidOnClosingDate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_PerformanceBasedRestrictedCommonStockMember" name="PerformanceBasedRestrictedCommonStockMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_PeriodDeferredCashPaymentIsDueAfterClosingOfAcquisition" name="PeriodDeferredCashPaymentIsDueAfterClosingOfAcquisition" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_PostClosingPurchasePriceAdjustments" name="PostClosingPurchasePriceAdjustments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="csgp_ProceedsFromExerciseOfStockOptionsAndEspp" name="ProceedsFromExerciseOfStockOptionsAndEspp" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="csgp_PropertyPlantAndEquipmentDirectTransactionCostsIncludedInBasis" name="PropertyPlantAndEquipmentDirectTransactionCostsIncludedInBasis" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="csgp_PropertyPlantAndEquipmentEstimatedUsefulLivesTableTextBlock" name="PropertyPlantAndEquipmentEstimatedUsefulLivesTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_PurchaseAndSalesLeasebackTransactionOfBuildingTextBlock" name="PurchaseAndSalesLeasebackTransactionOfBuildingTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_PurchaseOfBuildingAbstract" name="PurchaseOfBuildingAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_PurchaseOfBuildingTextBlock" name="PurchaseOfBuildingTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_PurchasePriceAllocationAxis" name="PurchasePriceAllocationAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_PurchasePriceAllocationDomain" name="PurchasePriceAllocationDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_ReactionWebMember" name="ReactionWebMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_RecentAccountingPronouncementsPolicyTextBlock" name="RecentAccountingPronouncementsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ReclassificationPolicyPolicyTextBlock" name="ReclassificationPolicyPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_ReconciliationOfSegmentLiabilitiesToTotalLiabilitiesAbstract" name="ReconciliationOfSegmentLiabilitiesToTotalLiabilitiesAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_RestructuringReserveAdjustmentSubleaseRevenueAndAccretion" name="RestructuringReserveAdjustmentSubleaseRevenueAndAccretion" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="csgp_RevolvingCreditFacilityForLettersOfCredit" name="RevolvingCreditFacilityForLettersOfCredit" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="csgp_RevolvingCreditSubFacilityForSwingLineLoans" name="RevolvingCreditSubFacilityForSwingLineLoans" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="csgp_SaleLeasebackTransactionExpense" name="SaleLeasebackTransactionExpense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="csgp_SaleLeasebackTransactionGrossProceedsDesignatedForTenantImprovement" name="SaleLeasebackTransactionGrossProceedsDesignatedForTenantImprovement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="csgp_SaleLeasebackTransactionGrossProceedsHeldInEscrow" name="SaleLeasebackTransactionGrossProceedsHeldInEscrow" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_SaleOfOfficeBuildingMember" name="SaleOfOfficeBuildingMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ScheduleOfUnrecognizedTaxBenefitsTableTextBlock" name="ScheduleOfUnrecognizedTaxBenefitsTableTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_SecondExcessCashFlowRepaymentPercentage" name="SecondExcessCashFlowRepaymentPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_SecondExcessCashFlowRepaymentRequirement" name="SecondExcessCashFlowRepaymentRequirement" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_SegmentReportingSegmentGrossAssets" name="SegmentReportingSegmentGrossAssets" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="csgp_SharebasedCompensationSharesOutstandingUnderStockOptionPlansExercisePriceRangeMaximum" name="SharebasedCompensationSharesOutstandingUnderStockOptionPlansExercisePriceRangeMaximum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_SharebasedCompensationSharesOutstandingUnderStockOptionPlansExercisePriceRangeMinimum" name="SharebasedCompensationSharesOutstandingUnderStockOptionPlansExercisePriceRangeMinimum" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_SharesOfCompanysCommonStockPurchasedDuringPeriod" name="SharesOfCompanysCommonStockPurchasedDuringPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_ShortTermInvestmentsMaturityTerm" name="ShortTermInvestmentsMaturityTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_SignificantCustomerRevenueThresholdPercent" name="SignificantCustomerRevenueThresholdPercent" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_SignificantCustomersPolicyTextBlock" name="SignificantCustomersPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_StockBasedCompensationExpenseAbstract" name="StockBasedCompensationExpenseAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_StockIncentivePlan1998Member" name="StockIncentivePlan1998Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_StockIssuedDuringPeriodNewIssuesCostPerShareShare" name="StockIssuedDuringPeriodNewIssuesCostPerShareShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_StockOptionsAndRestrictedStock" name="StockOptionsAndRestrictedStock" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_SubscriptionBasedLicensingAgreementMinimumTermYears" name="SubscriptionBasedLicensingAgreementMinimumTermYears" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_SummaryOfSignificantAccountingPoliciesLineItems" name="SummaryOfSignificantAccountingPoliciesLineItems" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_SummaryOfSignificantAccountingPoliciesTable" name="SummaryOfSignificantAccountingPoliciesTable" nillable="true" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_SwinglineLoanMember" name="SwinglineLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_TermOfConsentOrderPublicCommentPeriod" name="TermOfConsentOrderPublicCommentPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_ThirdExcessCashFlowRepaymentPercentage" name="ThirdExcessCashFlowRepaymentPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_ThirdExcessCashFlowRepaymentRequirement" name="ThirdExcessCashFlowRepaymentRequirement" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="csgp_TotalDeferredIncomeTaxPerYear" name="TotalDeferredIncomeTaxPerYear" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_TotalPurchasePriceMember" name="TotalPurchasePriceMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_TotalSegmentLiabilities" name="TotalSegmentLiabilities" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_UnitedStatesMember" name="UnitedStatesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="csgp_UsGovernmentSponsoredEnterpriseObligationsFairValueDisclosure" name="UsGovernmentSponsoredEnterpriseObligationsFairValueDisclosure" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element abstract="true" id="csgp_VirtualPremiseMember" name="VirtualPremiseMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="csgp_WhiteMarshOfficeConsolidationMarylandMember" name="WhiteMarshOfficeConsolidationMarylandMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
</xsd:schema>
