<SUBMISSION>
<ACCESSION-NUMBER>0001209191-07-015767
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20070301
<FILING-DATE>20070305
<DATE-OF-FILING-DATE-CHANGE>20070305
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>Columbia Equity Trust, Inc.
<CIK>0001316710
<ASSIGNED-SIC>6798
<IRS-NUMBER>201978579
<STATE-OF-INCORPORATION>MD
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>1750 H STREET, N.W.
<STREET2>SUITE 500
<CITY>WASHINGTON
<STATE>DC
<ZIP>20006
<PHONE>(202) 303-3060
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1750 H STREET, N.W.
<STREET2>SUITE 500
<CITY>WASHINGTON
<STATE>DC
<ZIP>20006
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>Vasvari Hal A
<CIK>0001330897
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-32536
<FILM-NUMBER>07673193
</FILING-VALUES>
<BUSINESS-ADDRESS>
<PHONE>202-303-3060
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>1750 H STREET, SUITE 500
<STREET2>COLUMBIA EQUITY TRUST, INC.
<CITY>WASHINGTON
<STATE>DC
<ZIP>20006
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>doc4.xml
<DESCRIPTION>FORM 4 SUBMISSION
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-03-01</periodOfReport>

    <notSubjectToSection16>1</notSubjectToSection16>

    <issuer>
        <issuerCik>0001316710</issuerCik>
        <issuerName>Columbia Equity Trust, Inc.</issuerName>
        <issuerTradingSymbol>COE</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001330897</rptOwnerCik>
            <rptOwnerName>Vasvari Hal A</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>1750 H STREET, N.W., SUITE 500</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>WASHINGTON</rptOwnerCity>
            <rptOwnerState>DC</rptOwnerState>
            <rptOwnerZipCode>20006</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>LTIP Units</value>
                <footnoteId id="F1"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2007-03-01</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>D</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>4000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>19.50</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2006-07-05</value>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F1"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Units</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">LTIP Units are convertible into units of limited partnership interest of Columbia Equity, LP (&quot;Units&quot;) on a one-for-one basis.  These expire upon dissolution or expiration of the term of Columbia Equity, LP, whichever occurs first.</footnote>
        <footnote id="F2">Disposed of for $19.50 in cash pursuant to a merger agreement.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ John S. Schissel
Attorney-in-Fact</signatureName>
        <signatureDate>2007-03-05</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
