Focus : Double Talk : POP QUIZ: NAME TWO ACTRESSES WITH NEW CHAT SHOWS. CLUES: ‘THREE’S’ A THIGHMASTER AND AN ‘EVENING’ AFTER ‘TAXI’

Suzanne Somers and Marilu Henner have more than a few things in common.

They’re both veteran sitcom actresses--”Three’s Company” and “Step by Step” for Somers and “Taxi” and “Evening Shade” for Henner. They’ve both written revealing books about their personal lives. They both have big, white toothy smiles and blue eyes with crinkles in the corners.

And in their 40s, they’re enviably fit. For Somers, 47, white flour is off limits, and yes, she really uses the Thighmaster, the exercise gizmo she pitches. Henner, 42, who despite having a baby a few months ago looks anything but postpartum, describes her dietary regime: “No dairy, no chicken, no meat, no shellfish, no sugar, no chemicals.”

There’s more. They’re both mothers to sons (Somers’ son Bruce is 30, Henner’s son Nicholas is 4 months old), as well as stepmothers. They’re married to producers (Somers to Alan Hamel; Henner to Rob Lieberman). They’re extremely open--Somers talks freely about growing up with an alcoholic father. In her book, Henner tells all about her intimate relationships with John Travolta and other celebs.

They’ve both spent years as guests on the talk circuit--from Carson to Letterman to Leno. Somers says she’s still trying to get over a recent raunchy chat with Howard Stern.

Now, these women are hosts themselves. “The Suzanne Somers Show” and “Marilu” were launched on the same September day--adding two new voices to the already cacophonous daytime talk-show arena.

When you’ve been in show biz for years and you’ve done the sitcoms, the movies and, for Somers, the Vegas act, is syndicated talk-show hostdom the only place left to go? Both Somers, who will continue to star on ABC’s “Step by Step” while doing her new show, and Henner insist that talk is not an ending point, but a new beginning.

“I feel like this is something I was born to do,” says Henner, still enthusiastic at 9:30 p.m. after a day of taping shows back to back. She has believed in the power of talk since the Henner clan held family meetings when she was young. “I’ve always felt that life is like a talk show.”

Somers says that life has prepared her to do a talk show. “I think it was the comedy background. I think it was the lecture circuit. It think it was writing books,” she explains. “I’ve lived--I have perspective.”

Will her perspective be enough to set her show apart from the crowded talk-show field? Both Somers and Henner say that their shows will tweak the genre.

Somers’ game plan “is to take a main celebrity guest and build a show around the guest.”

Here’s how it works: On a recent day on the Universal Studios set, Somers’ guest is actress Susan Dey, whose mother died when Dey was 9. The topic is daughters whose mothers have died. The author of the book “Motherless Daughters” joins in. During the show, both Dey and Somers get teary.

“Did you feel differently about Susan Dey?” Somers asks later in her dressing room. If the answer is yes, she’s accomplished her show’s goal.

Since celebrity chat is far from unique, Somers is relying on her own style. “The show is also me,” she says. “I have a point of view. And I like to understand what makes people tick because I’ve spent most of my life so far trying to understand what makes me tick.”

Although Henner’s show is more traditional talk in the Winfrey/Donahue style, she also says that her personality will make or break it. “I’m not looking to be an actress who’s been cast in the role of talk-show host,” she says.

So how do you personalize already-been-done topics like body image and stepparenting? Throw in those anecdotes. On the show about body image, Henner shares a picture of herself 50 pounds heavier. And when former “Taxi” co-star Tony Danza comes on, she teases him about a “tuft” of hair he has on his back.

Even the show’s topics are an outgrowth of Henner’s interests. “We did one on breast-feeding, one on the biological clock. I spent three years trying to have a baby, so I know a lot about that subject.”

There have been some uncomfortable growing pains behind the scenes at “Marilu,” however. Executive producer Mary Ellen DiPrisco left the staff after the first episode aired on Sept. 12, but no one on staff will talk about it.

Henner, too, is making some adjustments to talk. At a recent taping of a show on child performers, she makes heavy use of the TelePrompTer for her lines until she begins to loosen up. Later, she says, “I think the more you do it, the more natural you get at it.” While Henner isn’t worried that talk will put a damper on her acting career, Somers is more hesitant. “I wonder if I’ll become such a celebrity out of this that I’ll be forgotten as an actress,” she says, then reconsiders. “It didn’t happen with the Thighmaster.”

“Marilu” airs weekdays at 9 a.m. on KNBC. “The Suzanne Somers Show” airs weekdays at 1 p.m. on KCOP.