NEW YORK — Proving himself to be the substitute anchor with staying power, CNN’s Anderson Cooper has been handed his own evening news show.

The news cabler has announced that Cooper’s one-hour show will air at 7 p.m. EDT, while Paula Zahn’s new primetime newscast will air from 8-9 p.m. EDT.

Zahn returned to the set Monday night after a six-week hiatus. (Cooper has been her sub.)

There was still no word, though, about the exact format of either show as CNN tries to steer away from the personality-driven programming pursued by former CNN topper Walter Isaacson and return more to its hard-news roots.

“Both programs will roll out on air over the coming weeks and months, but, in the meantime, we are thrilled to have our evening and primetime anchors in their permanent positions,” CNN/U.S. exec producer Teya Ryan said.

Competitors pounced on the announcement as further evidence that CNN continues to flounder. They questioned the wisdom of having four news anchors on the nighttime sked –Lou Dobbs, Cooper, Zahn and Aaron Brown.

All the while, Fox News Channel continues to trounce CNN and MSNBC in the ratings.

Generally speaking, neither Cooper nor Zahn has been able to claim a ratings surge in the evenings.

Still, Cooper has been drawing kudos for his upbeat style and energy. The son of Gloria Vanderbilt, he has dabbled in both entertainment and news, serving as the original host of ABC’s “The Mole.”

Last fall, CNN execs apparently asked Cooper to make a choice between continuing his gig as a reality host and his job as a reporter-anchor for the news cabler.

Cooper, who previously worked for ABC News, decided to stick with the news biz.

“Anderson Cooper has done stellar work for CNN since he joined our network two years ago,” Ryan said. “Anderson is a wonderful writer and an excellent anchor, and we are delighted to have a home for him in our weekday lineup.”

It had been unclear until Monday whether Zahn’s evening show would run a full two hours, from 7-9 p.m.

The 8 p.m. EDT slot opened up in March when CNN cancelled Connie Chung’s talkshow. At the same time, the net bumped back “Crossfire” from 7 to 4:30 p.m.

Two hours too much

When moving from CNN’s ayem show to nighttime, Zahn made it clear that a two-hour primetime newscast would be difficult to pull off. Her new exec producer, Jim Miller, who comes from more of an entertainment background, reinforced this view.

“I am thrilled that everyone has come around to my way of thinking. I think that primetime television is a much different venue than morning television. The goal in primetime is to get people to stick with you,” Zahn said.

“You don’t see two-hour sitcoms,” Zahn said.

Zahn said her shows will definitely be news-driven. Monday, she focused on the U.S. Supreme Court’s landmark decision upholding affirmative action and hosted a discussion with former New York Mayor Rudolph Giuliani on anti-Semitism.

(Josef Adalian in Los Angeles contributed to this report.)