They walked the red carpet Friday night at Radio City Music Hall amid a media circus angling for glamour shots of other stars including Fergie, Rihanna, Chris Brown and the "Gossip Girl" gang.

Brown, the R&B heartthrob, soaked up all the attention with a smile as he showed off his dapper ensemble of a black vest and shirt, gray pants, shiny shoes and diamond stud earrings.

"To be a musician and a great entertainer, you have to be a trendsetter. To be a trendsetter, you have to know fashion — and I have fun with it," explained the singer, who later changed into khakis and a black shirt and scarf for a performance of his hit song "Forever."

The event will air Tuesday in a two-hour special on CBS. Proceeds will benefit Stand Up To Cancer, a program established by the Entertainment Industry Foundation to raise money for cancer research.

Stand Up To Cancer held a live telethon that aired simultaneously on ABC, NBC and CBS on Friday night.

Fashion Rocks provided a live feed to the fundraising show of a performance of more than a dozen divas — including Beyonce, Mariah Carey, Natasha Bedingfield, Fergie, Rihanna and Cyrus — who gathered on stage to sing their new charity song, "Just Stand Up." Theron and fellow Oscar winner Hilary Swank introduced the ladies' collaboration.

Bedingfield said she lost her grandmother to the disease several years ago, and was thrilled to share the spotlight with the other singers.

"This is the first time we're all together singing the song," she said backstage. "It was really special. It was really like a sisterhood, like a bond. ... We're all used to being the stars — the only star in the room — and it was really nice I think that everyone could just come together and really support each other."

Other performers included Timberlake, Kid Rock, Keith Urban, Duffy, the Pussycat Dolls and the Black Eyed Peas.

A highlight was Timberlake and Beyonce's sizzling duet of "Ain't Nothing Like the Real Thing," which channeled the soulful sound of the classic song's original singers, Marvin Gaye and Tammi Terrell.

Stars mingled and sipped cocktails backstage in the green room, where Leighton Meester of the CW teen drama "Gossip Girl" and her actor-beau Sebastian Stan hung out before she introduced Duffy's performance of "Mercy."

Meester's "Gossip" co-star Chace Crawford chatted up actress Hayden Panettiere, who embraced her rock-star side in a silver Ferragamo minidress and black heels.

"I usually try to mix class and then really funk it out," Panettiere said of her personal style. "It's rock meets class. I try — not always succeed, but I try."