Bill Demas, CEO of automated ad buying platform Turn, is leaving the company.

Mr. Demas, who has served as CEO of Turn since 2008, will stay on until a replacement is found. The departure, announced internally yesterday, was a mutual decision between Mr. Demas and the board, according to a spokeswoman. Mr. Demas will remain on the board.

"Bill has been our CEO for six and a half years and has done an incredible job," said Paul Alfieri, senior VP-marketing at Turn, in an interview. "After a successful run and as part of trying to make this an orderly transition, he and the board decided that it was time for a successor."

Turn raised $80 million early last year, but much has changed in the ad-tech landscape since then. Perhaps most strikingly, Wall Street has turned on ad-tech, sending shares down and tempering the industry's enthusiasm for the public markets. After six ad-tech IPOs from June 2013 to July 2014, there has only been once since. The difficult environment has led to falling ad-tech M&A deal prices as well.

Mr. Demas has talked openly of Turn's potential for an IPO, a move typical of firms taking on so much venture capital money, but the company remains private. Mr. Alfieri said the lack of exit is not responsible for Mr. Demas' departure. "Bill built a profitable and sustainable company. And we're growing, end of story," he said.

In recent weeks, Turn also hired its first ever chief revenue officer, Wendy MacGregor. Most recently at AOL, Ms. MacGregor said in an email that she's excited to join the company. "What I've found at Turn is a passionate team of experts that really understand how to help marketers connect more deeply with their audiences," she said.

Mr. Demas marks the second high-profile ad-tech CEO departure in recent months. George John, CEO of Rocket Fuel, stepped down from the role last month.

Contributing: Tim Peterson