Thompson will head account management and look after the agency's new-business effort.
The move reunites Thompson with CDD's joint creative directors, Walter Campbell, Dave Dye and Sean Doyle, his former colleagues at Abbott Mead Vickers BBDO.
He returns to the UK after an 18-month spell in Australia, where he was Publicis Mojo's communications director, overseeing the agency's Toyota and Procter & Gamble clients, among others.
Casper Thykier, the managing director at CDD, said: "Gav's one of those few talented people out there we were really keen to make part of the team. He adds more weight to the agency."
Thompson relocated to Australia in 2003 after resigning as TBWA\London's managing partner and account management group head, running Hutchinson 3. He also worked on Sony PlayStation, Ask Jeeves and Absolut.
Before that he was briefly the joint head of strategic planning at MVBMS/Euro RSCG and the group planning director at BBDO New York.
He launched his advertising career at AMV and went on to run the agency's Volvo and Guinness accounts.