    <SEC-DOCUMENT>0001999371-25-010348-index.html : 20250731
    <SEC-HEADER>0001999371-25-010348.hdr.sgml : 20250731
    <ACCEPTANCE-DATETIME>20250731130002
    ACCESSION NUMBER:		0001999371-25-010348
    CONFORMED SUBMISSION TYPE:	N-CSRS
    PUBLIC DOCUMENT COUNT:		19
    CONFORMED PERIOD OF REPORT:	20250531
    FILED AS OF DATE:		20250731
    DATE AS OF CHANGE:		20250731
    EFFECTIVENESS DATE:		20250731

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Flaherty & Crumrine PREFERRED & INCOME OPPORTUNITY FUND INC
    		CENTRAL INDEX KEY:			0000882071
    		ORGANIZATION NAME:
    		EIN:				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:		251170660

    	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 800
    		STREET 2:		C/O FLAHERTY & CRUMRINE INC
    		CITY:			PASADENA
    		STATE:			CA
    		ZIP:			91101

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	Flaherty & Crumrine PREFERRED INCOME OPPORTUNITY FUND INC
    		DATE OF NAME CHANGE:	20050708

    	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_053125.htm
    <DESCRIPTION>CERTIFIED SEMI-ANNUAL SHAREHOLDER REPORT
    <TEXT>
    Document 1 - file: pfo-ncsrs_053125.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.CERT
    <SEQUENCE>2
    <FILENAME>ex99cert.htm
    <DESCRIPTION>SECTION 302 CERTIFICAITON
    <TEXT>
    Document 2 - file: ex99cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.906 CERT
    <SEQUENCE>3
    <FILENAME>ex99906cert.htm
    <DESCRIPTION>SECTION 906 CERTIFICAITON
    <TEXT>
    Document 3 - file: ex99906cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.SCH
    <SEQUENCE>4
    <FILENAME>pfo-20250531.xsd
    <DESCRIPTION>XBRL SCHEMA FILE
    <TEXT>
    Document 4 - file: pfo-20250531.xsd

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.PRE
    <SEQUENCE>5
    <FILENAME>pfo-20250531_pre.xml
    <DESCRIPTION>XBRL PRESENTATION FILE
    <TEXT>
    Document 5 - file: pfo-20250531_pre.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.DEF
    <SEQUENCE>6
    <FILENAME>pfo-20250531_def.xml
    <DESCRIPTION>XBRL DEFINITION FILE
    <TEXT>
    Document 6 - file: pfo-20250531_def.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-101.LAB
    <SEQUENCE>7
    <FILENAME>pfo-20250531_lab.xml
    <DESCRIPTION>XBRL LABEL FILE
    <TEXT>
    Document 7 - file: pfo-20250531_lab.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>pfo-ncsrs_053125img004.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: pfo-ncsrs_053125img004.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>pfo-ncsrs_053125img001.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: pfo-ncsrs_053125img001.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>pfo-ncsrs_053125img002.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: pfo-ncsrs_053125img002.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>pfo-ncsrs_053125img003.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: pfo-ncsrs_053125img003.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>13
    <FILENAME>R1.htm
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 13 - file: R1.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>14
    <FILENAME>Show.js
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 14 - file: Show.js

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>15
    <FILENAME>report.css
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 15 - file: report.css

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>17
    <FILENAME>FilingSummary.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 17 - file: FilingSummary.html

    Document 17 - RAW XML: FilingSummary.xml

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>JSON
    <SEQUENCE>19
    <FILENAME>MetaLinks.json
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 19 - file: MetaLinks.json

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>ZIP
    <SEQUENCE>20
    <FILENAME>0001999371-25-010348-xbrl.zip
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 20 - file: 0001999371-25-010348-xbrl.zip

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>XML
    <SEQUENCE>21
    <FILENAME>pfo-ncsrs_053125_htm.xml
    <DESCRIPTION>IDEA: XBRL DOCUMENT
    <TEXT>
    Document 21 - file: pfo-ncsrs_053125_htm.html

    Document 21 - RAW XML: pfo-ncsrs_053125_htm.xml

    </DOCUMENT>
    </SEC-DOCUMENT>