CBC senior executive Kirstine Stewart is leaving the corporation to oversee the new Canadian office of Twitter.
Stewart has been CBC's executive vice-president of English language services, heading all television, radio and online services, since her appointment in January 2011.
She is leaving the position immediately to join Twitter, an internet social networking and microblogging service based in San Francisco.
"I've had some of the happiest moments in my life at the CBC, and I've been honoured to represent such an important name to Canadians," Stewart said in a release.
"I'm proud of what we've done together these past seven years. I will miss the CBC family dearly, but I know that even when one leaves the CBC, the CBC never really leaves you. It's in my DNA, and I'm all the better for it."
Hubert Lacroix, president and CEO of CBC/Radio Canada, credited Stewart with helping raise the corporation's profile.
"Kirstine really understands the role of the public broadcaster and has been a fierce proponent of its distinctive place," Lacroix said. "She has been instrumental in establishing CBC as a modern public broadcaster."
Looking ahead to CBC's coverage of high-profile events such as the Olympics, the Pan American Games and soccer's World Cup in Brazil, Lacroix said a recruitment process has been launched for Stewart's replacement.
In the meantime, Neil McEneaney, general manager, finance and strategy, will fill in for Stewart on an interim basis.