The actors may be wearing costumes – and/or robes and hospital gowns.

But that’s cool, because the audience dresses the same way.

“Only Make Believe”was created by actress/director/writer/ Dena Hammerstein four years ago to honor her late husband, producer/director James Hammerstein. He was the son of famed composer Oscar Hammerstein.

“I wanted to create something that would be a wonderful tribute to him,” she said.

James Hammerstein died in 1999. Shortly afterward, Dena Hammerstein, who had long volunteered at the pediatric unit at NYU Medical Center’s Rusk Institute, started taking sick children from the hospital on day trips to the Theatre District.

Logistics proved difficult, both for organizers charged with getting the children – some of them in wheelchairs – to performances and on the children themselves.

“They would come back to the hospital wiped out,” Hammerstein said. “They had a good time, but they were exhausted.”

So she decided to take the theatre to the children.

“Only Make Believe” teams, each composed of three professional actors, hold weekly theater workshops in hospital pediatric wards.

The program employs a multiethnic, multilingual troupe of actors, Hammerstein said.

The troupe enlists the patients – some of whom have cancer, HIV, cerebral palsy, autism, chronic depression or physical disabilities – as both audience members and performers.

Children are involved in every stage of the production. Hammerstein, who with her staff writes most of the plays, said she has been known to tweak the dialogue if youngsters think it’s not hip or dead-on.

And admittedly, most adults could use some dialogue help when they’re doing hip-hop versions of “The Emperor’s New Clothes” and other plays to keep children interested and involved.

“We try to do adaptations of folk tales or stories that they already know,” Hammerstein said. “We did ‘Sleeping Beauty,’ but in this one she was a complete brat and everyone wanted her to go back to sleep. This way, these plays are special for these children,” she said.

At the end of six weeks, the actors and new actors put on a show for family and hospital friends. When the troupe moves on, the props stay behind.

Hammerstein said she has watched once-reclusive children blossom because of their involvement in the production. “Every child is applauded, whatever part they play,” she said. I’ve seen children who were completely withdrawn, standing to one side when we start, who are in the front rows acting and having a great time by the time we are done.

“By giving them the freedom to express themselves in a way they haven’t before, you just watch them grow and just shine.”

“Only Make Believe” has mounted productions in 134 area hospitals: Bellevue Hospital, Brooklyn Hospital, Elmhurst Hospital Center, Foundling Hospital, Harlem Hospital Center, Incarnation Children’s Center, Kings County Hospital, Lincoln Hospital, Maimonides Medical Center, Metropolitan Hospital Center, Mount Sinai Hospital, New York Hospital Center and St. Mary’s Hospital for Children.

Hammerstein hopes one day to mount productions in every pediatric ward in the city.

In June, the United Hospital Fund’s New Leadership Group honored Hammerstein and the “Only Make Believe” program.