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Proc-Type: 2001,MIC-CLEAR
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<SEC-DOCUMENT>0001255452-06-000002.txt : 20061228
<SEC-HEADER>0001255452-06-000002.hdr.sgml : 20061228
<ACCEPTANCE-DATETIME>20061228122938
ACCESSION NUMBER:		0001255452-06-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20061226
FILED AS OF DATE:		20061228
DATE AS OF CHANGE:		20061228

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Flaherty & Crumrine PREFERRED INCOME OPPORTUNITY FUND INC
		CENTRAL INDEX KEY:			0000882071
		IRS NUMBER:				954355600
		STATE OF INCORPORATION:			MD
		FISCAL YEAR END:			1130

	BUSINESS ADDRESS:	
		STREET 1:		301 E COLORADO BLVD STE 720
		STREET 2:		C/O FLAHERTY & CRUMRINE INC
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91101
		BUSINESS PHONE:		(626) 795-7300

	MAIL ADDRESS:	
		STREET 1:		301 COLORADO BLVD STE 720
		STREET 2:		C/O FLAHERTY & CRUMRINE INC
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91101

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PREFERRED INCOME OPPORTUNITY FUND INC
		DATE OF NAME CHANGE:	19920929

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			STONE BRADFORD S
		CENTRAL INDEX KEY:			0001255452

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	811-06495
		FILM NUMBER:		061302110

	BUSINESS ADDRESS:	
		STREET 1:		FLAHERTY & CRUMRINE INC
		STREET 2:		392 SPRINGFIELD AVE MEZZANINE SUITE
		CITY:			SUMMIT
		STATE:			NJ
		ZIP:			07901
		BUSINESS PHONE:		9089180300

	MAIL ADDRESS:	
		STREET 1:		392 SPRINGFIELD AVE MEZZANINE SUITE
		CITY:			SUMMIT
		STATE:			NJ
		ZIP:			07901
</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>2006-12-26</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000882071</issuerCik>
        <issuerName>Flaherty &amp; Crumrine PREFERRED INCOME OPPORTUNITY FUND INC</issuerName>
        <issuerTradingSymbol>PFO</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001255452</rptOwnerCik>
            <rptOwnerName>STONE BRADFORD S</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>392 SPRINGFIELD AVE MEZZANINE SUITE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>SUMMIT</rptOwnerCity>
            <rptOwnerState>NJ</rptOwnerState>
            <rptOwnerZipCode>07901</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2006-12-26</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>J</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>8603</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>12.3</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8603</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>Please see footnote 1</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">Mr. Stone is a 10% shareholder of Flaherty &amp; Crumrine Incorporated, the direct beneficial owner of these shares. On December 26, 2006, the Board of Directors of Flaherty &amp; Crumrine determined that Mr. Stone, as a director, would share investment control of these shares with the other directors of the corporation. Consequently, Mr. Stone is now reporting his pecuniary interest in these shares because he is no longer entitled to rely on Rule 16a-1(2)(iii) under the Exchange Act.</footnote>
        <footnote id="F2">Mr. Stone directly holds an additional 4,000 shares of the Fund.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Bradford S. Stone</signatureName>
        <signatureDate>2006-12-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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