Mottola resigned under fire Thursday. His departure comes after 14 years at the company. He joined the company in 1987, when it was known as CBS Records. Sony has agreed to release him from his contract two years early.
Lack, 55, has been president and chief operating officer of NBC for the past 18 months. He also served as president of the network's News Division for eight years. He also worked at CBS for 17 years. Lack has no experience in the music industry.
He is a close friend of Howard Stringer, who heads Sony's U.S. operations.
The New York Times first reported Lack was moving to Sony in its online edition.
Sony enjoyed several high-profile, multiplatinum hits from acts including Bruce Springsteen, Mariah Carey, Dion and the Dixie Chicks last year; it garnered numerous Grammy nominations on Tuesday, including several in the major categories.
But Sony is third among the five major music labels in terms of market share; it had 15.24 percent of the album market in 2002, a dip from 15.83 percent in 2001.
Last year, Mottola also was involved in an embarrassing feud with one of Sony's biggest stars, Michael Jackson. Jackson, disappointed with below-average sales and a perceived lack of promotion for his album, "Invincible," publicly accused Mottola of being a racist. Several black industry executives spoke in Mottola's defense.
Among Mottola's biggest successes was Mariah Carey; he signed the unknown when he was president of Columbia Records. Carey made her debut in 1990 and went on to sell more than 50 million albums.
Carey and Mottola wed in 1993 and split up after four years. She left Columbia in 2001, expressing dissatisfaction with the promotion of her music there.
Another artist who benefited from Mottola's marketing skill was Jennifer Lopez, who was known as an actress and dancer but not a singer when she was signed to Epic Records by Mottola. All of her releases have sold at least 1 million copies.
In recent months, Mottola had embarked on marketing strategies to link its superstars with brands to boost sales. For example, Dion will soon be featured in ads for Chrysler; Destiny's Child lead singer Beyonce Knowles is the new pitchwoman for Pepsi.