Keenan will work closely with Dave King, the managing director of the division. However, King will continue to report to Emap's chief executive Tom Moloney.
Keenan fills the gap left by Tim Schoonmaker, the former Emap Performance chief executive, who quit in January.
Emap Advertising launched in April 2000 to offer media solutions across the Emap portfolio. Keenan has been briefed to continue the development of the division along these lines.
Emap Advertising has worked with brands including Wella, NatWest, Mars and BT. An ongoing tie-up with Scottish Courage's Foster's uses Emap's radio platforms as well as its mens' monthly FMH and FHM.com website.
Keenan said: "Emap Advertising is an innovator. It is also hugely ambitious and driven to embed changes for the better in the way business is conducted. I am excited at being part of this team, which is determined to continue to deliver, to beat the market, to be famous for creativity and new thinking."
King added: "We have worked closely with Paul for some time and he is the ideal person to chair Emap Advertising's board."