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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-03-26</periodOfReport>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001343754</rptOwnerCik>
            <rptOwnerName>Hamer Scott W</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>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>600</value>
                    <footnoteId id="F1"/>
                </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>17.50</value>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <exerciseDate>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-04-21</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4400</value>
                    <footnoteId id="F2"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4400</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeTransaction>
            <securityTitle>
                <value>Option Plan (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>23.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-03-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>800</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2017-03-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>800</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>800</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">On December 27, 2006, the common stock of the Issuer split 2-for-1, resulting in the reporting person's ownership of 300 additional shares of common stock.</footnote>
        <footnote id="F2">This option was previously reported as covering 2,200 shares at an option price of $35.00, but was adjusted to reflect the 2-for-1 stock split that occurred on December 27, 2006.</footnote>
        <footnote id="F3">As a result of the stock split and the vesting of certain of the options, options to purchase 950 shares of the common stock of the Issuer are currently exercisable.  The remaining options will become exercisable as follows: 350 on 4/21/2007; 400 on each of 4/21/2008 and 4/21/2009; 500 on each of 4/21/2010 and 4/21/2011; 600 on 4/21/2012 and the remaining 700 on 4/21/2013.</footnote>
        <footnote id="F4">The option to purchase shares of the  common stock of the Issuer will  become exercisable as follows:  50 on each of 3/26/2008, 3/26/2009, 3/26/2010, 3/26/2011 and 3/26/2012; 100 will become exercisable on 3/26/2013, 3/26/2014, 3/26/2015 and 3/26/2016; the remaining 150 will become exercisable on 3/26/2017.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Scott W. Hamer</signatureName>
        <signatureDate>2007-03-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
