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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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<SEC-DOCUMENT>0001254595-08-000014.txt : 20080527
<SEC-HEADER>0001254595-08-000014.hdr.sgml : 20080526
<ACCEPTANCE-DATETIME>20080527165848
ACCESSION NUMBER:		0001254595-08-000014
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20080522
FILED AS OF DATE:		20080527
DATE AS OF CHANGE:		20080527

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			FIRST POTOMAC REALTY TRUST
		CENTRAL INDEX KEY:			0001254595
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				371470730
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		7600 WISCONSIN AVENUE
		STREET 2:		11TH FLOOR
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
		BUSINESS PHONE:		3019869200

	MAIL ADDRESS:	
		STREET 1:		7600 WISCONSIN AVENUE
		STREET 2:		11TH FLOOR
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			HELLER J RODERICK III
		CENTRAL INDEX KEY:			0001227666

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-31824
		FILM NUMBER:		08861305

	BUSINESS ADDRESS:	
		STREET 1:		YORK INTERNATIONAL CORP.
		STREET 2:		631 SOUTH RICHLAND AVENUE
		CITY:			YORK
		STATE:			PA
		ZIP:			17403
		BUSINESS PHONE:		301-986-9200

	MAIL ADDRESS:	
		STREET 1:		C/O FIRST POTOMAC REALTY TRUST
		STREET 2:		7600 WISCONSIN AVENUE, 11TH FLOOR
		CITY:			BETHESDA
		STATE:			MD
		ZIP:			20814
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-05-22</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001254595</issuerCik>
        <issuerName>FIRST POTOMAC REALTY TRUST</issuerName>
        <issuerTradingSymbol>FPO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001227666</rptOwnerCik>
            <rptOwnerName>HELLER J RODERICK III</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O FIRST POTOMAC REALTY TRUST</rptOwnerStreet1>
            <rptOwnerStreet2>7600 WISCONSIN AVENUE, 11TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BETHESDA</rptOwnerCity>
            <rptOwnerState>MD</rptOwnerState>
            <rptOwnerZipCode>20814</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Shares</value>
            </securityTitle>
            <transactionDate>
                <value>2008-05-22</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>2500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.12</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>18000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Restricted common shares awarded by the Compensation Committee of the Board of Trustees that will vest on May 22, 2009.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Joel F. Bonder, Attorney in Fact for J. Roderick Heller, III</signatureName>
        <signatureDate>2008-05-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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