LOS ANGELES — Maura Tierney likes her new, pixie haircut.

“It dries faster,” she said, tugging at a curl behind her ear.

Mainly, though, she’s happy to have hair. After being diagnosed with breast cancer last year, Tierney, 45, had surgery and chemotherapy, dropping out of NBC’s “Parenthood” to do everything necessary to get well.

But as of this week, Tierney is back on television in ABC’s “The Whole Truth.” Lauren Graham replaced her in “Parenthood,” leaving Tierney free to take a role that was actually written for her.

Tom Donaghy created the character of Kathryn Peale, the no-nonsense lead prosecutor who matches wits with friend and adversary Jimmy Brogan (Rob Morrow), with Tierney in mind. Donaghy and Tierney have known each other since college, but she was committed to “Parenthood,” so he cast Joely Richardson.

Then real life intervened. While Tierney was finishing treatment and acting in a play in New York, Richardson asked to be released from “The Whole Truth.”

“Joely’s life was fairly complicated,” executive producer Jonathan Littman told TV critics when ABC introduced “The Whole Truth” in August. Richardson’s mother is actress Vanessa Redgrave, and three members of that family — Joely’s sister, Natasha Richardson; her uncle, Corin Redgrave; and her aunt, Lynn Redgrave — had died within 14 months of one another.

“It was the right thing to do, to let her go and deal with that,” Littman said. “The timing worked out great, because then Maura was available and able to do it.”

Tierney spent nine years on “ER,” leaving in 2008. Tough nurse Abby Cunningham, always determined not to look vulnerable, showed up a bit when Tierney was asked about her cancer.

“I’m good,” she said, adding, when pressed, “I’m healthy. … I read the script, and I liked it. So that was that.”

Tierney had chosen to return to theater, rather than television, because she said she appreciated the precision and structure that a play required.

“I wasn’t really thinking about doing another (TV) show,” she said. “But I really responded to the character that Tom wrote, I guess because (he) wrote it for me.”

Donaghy created the role in response to “a lot of female characters on television that weren’t strong in the way that I understand how women can be strong and also feminine,” he said.

“I knew Maura had the elegance, and we keep saying this word ‘wit,’ so I wrote it with her talents in mind, never thinking she would be available. So it’s quite a gift that she is.”

Added Tierney, “My ego’s not involved there at all. But I thought she was a really, really appealing character … and funny. And it was interesting to find a character that had such sort of a great sense of humor, yet was so driven.”

Tierney has been quoted as saying she was uncomfortable having to ask for help during her treatment, and she clearly would rather get past questions about how she was changed by the experience.

“I probably have a new perspective on everything, in general,” she said.

Still, “My perspective probably should change more than it has, quite honestly. But as far as work goes … it’s a priority for me now to be able to work with people who I really like and trust.”

Of Donaghy, she said, “Tom and I are friends, like actual real friends, not Hollywood friends. We went to college together. We’ve known each other for over 20 years. So that will be a factor because I feel like, yeah, it’s too much time involved of your life to not enjoy it.”

‘The Whole Truth’

When: 10 tonight

Where: ABC