<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2005-04-27</periodOfReport>

    <issuer>
        <issuerCik>0000921847</issuerCik>
        <issuerName>HUDSON CITY BANCORP INC</issuerName>
        <issuerTradingSymbol>HCBK</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001206752</rptOwnerCik>
            <rptOwnerName>SALAMONE DENIS J</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>WEST 80 CENTURY ROAD</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PARAMUS</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07652</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Senior Executive VP</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <transactionDate>
                <value>2005-04-27</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>I</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>1027</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>33.27</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1027</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By PIB</value>
                    <footnoteId id="F7"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By GRAT</value>
                    <footnoteId id="F6"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>92000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>55000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By IRA</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>40000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By Spouse</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock, par value $0.01/share</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4546</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By ESOP</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>39.20</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-02-18</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>100000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>100000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Stock Options (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>11.515</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-10-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>256000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>256000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Phantom Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F5"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F5"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F5"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5955</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5955</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Award to the reporting person of 15,000 shares of common stock pursuant to the Hudson City Bancorp, Inc. 2000 Recognition and Retention Plan (&quot;RRP&quot;), which the stockholders approved at a Special Meeting of Stockholders of Hudson City Bancorp, Inc. held on January 13, 2000 (&quot;Special Meeting&quot;), effective February 19, 2004. Such award will vest in equal installments, at a rate of 20% per year, on each of April 20, 2006, 2007, 2008, 2009 and 2010. Previous award to the reporting person of 100,000 shares of common stock pursuant to the Denis J. Salamone Restricted Stock Award Plan (&quot;the Plan&quot;), was made by the Board of Directors, effective November 9, 2001.  On April 20, 2002, 20,000 shares vested and became directly owned by the reporting person.  (Footnote 1 continues in footnote 2 below.)</footnote>
        <footnote id="F2">Footnote 1 continues:  The shares awarded pursuant to the Plan were adjusted to reflect a 2-for-1 stock split on June 17, 2002 and on each of April 20, 2003, 2004 and 2005 an additional 40,000 shares vested and became directly owned by the reporting person.  The 40,000 unvested shares will vest on April 20, 2006.  Such shares are subject to legend until vested.</footnote>
        <footnote id="F3">Grant to reporting person of options to buy 100,000 shares of common stock pursuant to the Hudson City Bancorp, Inc. 2000 Stock Option Plan, approved at the Special Meeting, was made by the Board of Directors, effective February 19, 2004. Such options will vest and become exercisable in equal installments, at a rate of 20% per year, on each of January 13, 2006, 2007,2008, 2009 and 2010.  Previous grant to the reporting person of options to buy 160,000 shares of common stock pursuant to the Stock Option Agreement for Denis J. Salamone was made by the Board of Directors, effective October 29, 2001.  Options to buy 32,000 shares of common stock vested and became exercisable on January 13, 2002.  (Footnote 3 continues in footnote 4 below.)</footnote>
        <footnote id="F4">Footnote 3 continues: The options awarded to the reporting person were adjusted to reflect a 2-for-1 stock split on June 17, 2002 and 64,000 options vested and  became exercisable on each of January 13, 2003, 2004 and 2005.  The 64,000 unvested options will vest and become exercisable on January 13, 2006.</footnote>
        <footnote id="F5">The reporting person is due upon retirement the equivalent dollar value of 5,955 shares of HCBK common stock on December 31, 2004 through the Hudson City Savings Bank ESOP Restoration Plan.</footnote>
        <footnote id="F6">The shares reported are held in a grantor retained annuity trust that was established for the benefit of the reporting person's children.  The reporting person is the grantor and the reporting person and his children serve as trustees.</footnote>
        <footnote id="F7">Shares are held in the reporting person's account in the Hudson City Savings Bank Profit Incentive Bonus Plan.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Louis J. Beierle, Attorney-in-fact</signatureName>
        <signatureDate>2005-04-28</signatureDate>
    </ownerSignature>
</ownershipDocument>
