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

    <schemaVersion>X0202</schemaVersion>

    <documentType>3</documentType>

    <periodOfReport>2005-07-27</periodOfReport>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0001123735</issuerCik>
        <issuerName>COMMUNITY FINANCIAL SHARES INC</issuerName>
        <issuerTradingSymbol>N/A</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001343924</rptOwnerCik>
            <rptOwnerName>Mucker William M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>COMMUNITY FINANCIAL SHARES, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>357 ROOSEVELT ROAD</rptOwnerStreet2>
            <rptOwnerCity>GLEN ELLYN</rptOwnerCity>
            <rptOwnerState>IL</rptOwnerState>
            <rptOwnerZipCode>60137</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>VP and Asst. Secretary</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Option Plan (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>35.00</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-02-13</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-02-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2200</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Options to purchase 300 shares of the common stock of the Issuer are currently exercisable.  The remaining options will become exercisable as follows:  175 on each of 2/13/2006 and 2/13/2007; 200 on each of 2/13/2008 and 2/13/2009; 250 on each of 2/13/2010 and 2/13/2011;  300 on 2/13/2012 and 350 on 2/13/2013.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/Scott W. Hamer as attorney-in-fact for William W. Mucker</signatureName>
        <signatureDate>2005-11-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
