Cable's MTV has marked its eighth straight first-quarter of growth, but is also seeing ratings decline, the Hollywood Reporter said Monday.

The numbers decline began when three of the Viacom-owned network's three powerhouse shows went off the air: "Newlyweds: Nick & Jessica," "The Ashlee Simpson Show" and "The Osbournes."

Cameron Diaz's new series "Trippin'" has gotten a tepid reception and Travis Barker of "Meet the Barkers" is not generating the interest Ozzy Osbourne did. Even MTV's most reliable standby, "The Real World," has cooled, the newspaper said.

Horizon Media Senior President of Research Brad Adgate said the network has a real challenge.

"It's difficult for MTV to target the teen market, which is very fluid," he said. "Once something becomes too popular, it goes out of vogue with teens. MTV always has to reinvent a new programming genre."

Meanwhile, Kagan Media projects the network will be the only cable property to bring in more than $1 billion in advertising revenue this year.