"After two years running Last.fm within CBS we feel the time is right to begin the process of handing over the reins," Martin Stiksel, Felix Miller and Richard Jones said in a joint blog post on Wednesday.
CBS Music Group's recently appointed president David Goodman is expected to serve as the site's interim general manager while the company seeks new management.
Based in New York, Goodman reports to CBS Interactive president Neil Ashe, while working closely with Dan Mason, president and chief executive of CBS Radio.
In May, CBS Corp. announced the formation of the CBS Interactive Music Group. Part of CBS Interactive, the new unit brought together CBS's digital music properties -- including Last.fm and CBS Radio's more than 100 music Web sites, online audio streams, and mobile applications.
The combined assets of the newly formed CBS Interactive Music Group reach approximately 40 million unique monthly users worldwide, according to CBS.
For Last.fm, the deal represented a substantial increase in the number of broadcast partners and breadth of content it could offer -- adding CBS Radio's 140 stations to its existing partnerships with Universal, EMI, Warner Music Group and Sony BMG, as well as about 150,000 independent artists and studios.
By its own estimate, Last.fm presently attracts 37.3 million monthly unique visitors.
The site, which CBS acquired for $280 million in mid-2007, offers users personalized track recommendations, concert updates and music videos based on which tracks they have listened to in the past. Using its "scrobbling" technology and reference engine, the site builds user profiles that are tailor-made for targeting advertising.
Last year, CBS helped Last.fm reach deals with Universal Music Group, Sony/BMG, Warner Music Group and EMI Group, among others, all in an effort to become the biggest free, ad-supported music service online.
In December, Last.fm laid off a fifth of its workforce, or some 20 employees.