Petersen, who will be 91 in May, lost one leg in an accident when he was volunteering in 2002 and the other later to a staph infection.
"I roll in there and I roll out, and on the way out, Hey, you got no legs. That's right, I didn't have 'em coming in either," said Woody.
For 28 years Petersen was a Navy pilot who retired from the service in 1970 as a captain in charge of the Navy's Chicago-area recruiting district.
Elsa, his wife of 64 years, says volunteering is the most important thing he does.
"He looks forward to his Tuesdays, always has stories to tell when he comes home. It's something he does all by himself. I'm not involved and that's good," said Elsa Petersen.
"We can say a lot of things to our patients, but when an actual patient comes in who has been here before comes and brings light to their day, I don't think you can find more value than that during your hospital stay," said Anne Spratt, recreational therapist.
"I get more out of giving 10 patients over here than I give, because they are all so receptive...people that work here are so caring, so giving of themselves, you can't but try to help these people look forward to a new life," Woody said.