<SEC-DOCUMENT>0001387131-17-003801-index.html : 20170728
<SEC-HEADER>0001387131-17-003801.hdr.sgml : 20170728
<ACCEPTANCE-DATETIME>20170728151623
ACCESSION NUMBER:		0001387131-17-003801
CONFORMED SUBMISSION TYPE:	N-CSRS
PUBLIC DOCUMENT COUNT:		7
CONFORMED PERIOD OF REPORT:	20170531
FILED AS OF DATE:		20170728
DATE AS OF CHANGE:		20170728
EFFECTIVENESS DATE:		20170728

FILER:

	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

	FILING VALUES:
		FORM TYPE:		N-CSRS
		SEC ACT:		1940 Act
		SEC FILE NUMBER:	811-06495
		FILM NUMBER:		17989708

	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>N-CSRS
<SEQUENCE>1
<FILENAME>pfo-ncsrs_053117.htm
<DESCRIPTION>SEMI-ANNUAL SHAREHOLDER REPORT
<TEXT>
Document 1 - file: pfo-ncsrs_053117.htm

</DOCUMENT>
<DOCUMENT>
<TYPE>EX-99.CERT
<SEQUENCE>2
<FILENAME>ex99-cert.htm
<DESCRIPTION>CERTIFICATIONS PURSUANT TO SECTION 302
<TEXT>
Document 2 - file: ex99-cert.htm

</DOCUMENT>
<DOCUMENT>
<TYPE>EX-99.906CERT
<SEQUENCE>3
<FILENAME>ex99-906cert.htm
<DESCRIPTION>CERTIFICATION PURSUANT TO SECTION 906
<TEXT>
Document 3 - file: ex99-906cert.htm

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>4
<FILENAME>pfoncsrs053117001.jpg
<DESCRIPTION>GRAPHIC
<TEXT>
Document 4 - file: pfoncsrs053117001.jpg

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>5
<FILENAME>pfoncsrs053117002.jpg
<DESCRIPTION>GRAPHIC
<TEXT>
Document 5 - file: pfoncsrs053117002.jpg

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>6
<FILENAME>pfoncsrs053117003.jpg
<DESCRIPTION>GRAPHIC
<TEXT>
Document 6 - file: pfoncsrs053117003.jpg

</DOCUMENT>
<DOCUMENT>
<TYPE>GRAPHIC
<SEQUENCE>7
<FILENAME>pfoncsrs053117004.jpg
<DESCRIPTION>GRAPHIC
<TEXT>
Document 7 - file: pfoncsrs053117004.jpg

</DOCUMENT>
</SEC-DOCUMENT>