LOS ANGELES -- Sherry Lansing, the one-time model and actress who broke down barriers for women in the movie industry as one of Hollywood's most powerful studio chiefs, said Tuesday she will leave her post as chairwoman of Paramount Pictures at the end of next year when her contract expires.

At Paramount, Lansing was a key player in the Oscar-winning blockbusters "Titanic," "Braveheart" and "Saving Private Ryan." But the studio has seen a string of flops and box office disappointments in recent years, including "The Stepford Wives."

"I'll have been in this job for 12 years and have had the opportunity and the privilege to work with the very best the entertainment industry has to offer," the 60-year-old Lansing said in a statement.

"But now it is time for new challenges."

Her announcement follows several management shake-ups at parent company Viacom Inc., including the departure of Jonathan Dolgen, who had shared power with Lansing at Paramount.

It also comes after several years of lackluster performance at Paramount and pledges by Viacom's management, including Viacom chairman Sumner Redstone, to revitalize the studio.

Lansing became the first female president of production for a Hollywood studio in 1980 when she was named to that job at 20th Century Fox Productions.

She later became a partner with producer Stanley Jaffe in 1983 and they made such films as "Fatal Attraction" and "The Accused." Jaffe was named president of the former Paramount Communications and in 1992 he made Lansing studio chief.

Lansing, who broke into Hollywood in the late 1960s after being a math teacher in Watts, has been a role model in the film industry. She helped pave the way for other female studio chiefs, including Columbia Pictures' Amy Pascal, Universal Pictures chairwoman Stacey Snider and the late Columbia Pictures head Dawn Steel.

Viacom shares rose 39 cents on the New York Stock Exchange to close at $37.12.