-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 M62UwZLohpMFyiY05MzKFbDiOtkTk4gcv8CfE7YUVGGonRRMF92n8tczmL7ARBd9
 tpkxNTkf6TFPBeb9CLv2/Q==

<SEC-DOCUMENT>0001252911-06-000003.txt : 20061228
<SEC-HEADER>0001252911-06-000003.hdr.sgml : 20061228
<ACCEPTANCE-DATETIME>20061228125714
ACCESSION NUMBER:		0001252911-06-000003
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20061226
FILED AS OF DATE:		20061228
DATE AS OF CHANGE:		20061228

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CHADWICK ROBERT E
		CENTRAL INDEX KEY:			0001252911

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	811-06495
		FILM NUMBER:		061302196

	BUSINESS ADDRESS:	
		BUSINESS PHONE:		6267957300

	MAIL ADDRESS:	
		STREET 1:		301 E COLORADO BLVD STE 720
		CITY:			PASADENA
		STATE:			CA
		ZIP:			91101

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
</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>0001252911</rptOwnerCik>
            <rptOwnerName>CHADWICK ROBERT E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>301 E COLORADO BLVD STE 720</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PASADENA</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>91101</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Vice President, CFO</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. Chadwick 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. Chadwick, as a director, would share investment control of these shares with the other directors of the corporation. Consequently, Mr. Chadwick 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. Chadwick directly holds an additional 2,821 shares of the Fund.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>R. Eric Chadwick</signatureName>
        <signatureDate>2006-12-27</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
-----END PRIVACY-ENHANCED MESSAGE-----
