Yahoo! CEO Jerry Yang, who has been back and forth on whether he was sticking with the struggling internet giant, chose to surprse everyone and quit on Monday, the New York Times and others wrote.

Yang, who was unclear about Yahoo!'s future last summer at the Herb Allen Sun Valley Media Conference. At the time, Yang told FBLA that is future was uncertain, but that for the short term he wasn't going anywhere.

In a memo sent to the company's staff on Monday evening, Yang said he would retain the post until the board names his successor. After that, he said he'd return to his previous job as "chief Yahoo" - a corporate strategy role - and remain on the board.

Yang's move comes 18 months after he assumed the CEO post after the departure of Terry Semel. His tenure has been dogged by a precipitously declining stock price and the collapse of a $44 billion takeover offer from Microsoft.

In the memo, Yang wrote, "I strongly believe that having transformed our platform and better aligned costs and revenues, we have a unique window for the right ceo to take ownership over the next wave of mission-critical decisions facing the company."