<?xml version="1.0"?><ownershipDocument><schemaVersion>X0101</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-07-02</periodOfReport><issuer><issuerCik>0000799166</issuerCik><issuerName>MASSBANK CORP</issuerName>        <issuerTradingSymbol>MASB</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001235351</rptOwnerCik><rptOwnerName>BEDELL MATHIAS  B</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>  </rptOwnerStreet1><rptOwnerStreet2>  </rptOwnerStreet2><rptOwnerCity>  </rptOwnerCity><rptOwnerState>  </rptOwnerState><rptOwnerZipCode>  </rptOwnerZipCode></reportingOwnerAddress><reportingOwnerRelationship><isDirector>1</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle></officerTitle><otherText></otherText></reportingOwnerRelationship></reportingOwner><derivativeSecurity><securityTitle><value>Deferred Compensation</value><footnoteId id="F1" /><footnoteId id="F2" /></securityTitle><conversionOrExercisePrice><value>30.06</value></conversionOrExercisePrice><transactionDate><value>2003-05-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>81.3578</value></transactionShares><transactionValue><value>30.06</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-07-01</value></exerciseDate><expirationDate><value>2003-07-01</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common</value></underlyingSecurityTitle><underlyingSecurityShares><value>81.357</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>10713.9488</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeSecurity><derivativeSecurity><securityTitle><value>Deferred Compensation</value><footnoteId id="F1" /></securityTitle><conversionOrExercisePrice><value>36.25</value></conversionOrExercisePrice><transactionDate><value>2003-07-01</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>41.3793</value></transactionShares><transactionValue><value>36.25</value></transactionValue><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2003-07-01</value></exerciseDate><expirationDate><value>2003-07-01</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common</value></underlyingSecurityTitle><underlyingSecurityShares><value>41.3793</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>10755.3281</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeSecurity><footnotes><footnote id="F1">Cash-only security issued pursuant to the Directors'Deferred Compensation Plan</footnote><footnote id="F2">Represents the reinvestment of dividends pursuant to the Directors' Deferred Compensation Plan</footnote></footnotes><ownerSignature><signatureName>David F. Carroll, Attorney-In-Fact for Mathias B. Bedell</signatureName><signatureDate>2003-07-02</signatureDate></ownerSignature></ownershipDocument>

