The mum and son who spent ten days lost in dense bushland used skills inspired by British adventurer and survival expert Bear Grylls to stay alive, a police officer said.

Michelle Pittman, 40, and her nine-year-old son Dylan were discovered stumbling along Mount Royal Road within the Mount Royal National Park in NSW at lunchtime on Thursday having been missing since Monday, October 2.

Rob Post, Hunter Valley LAC Acting Superintendent told Nine.com.au police had been tracking the two in the hours prior to their rescue.

"We had located their tracks on a creek bed and we were tracking them," Acting Supt Post said.

"Just prior to us find them they did crawl out onto the road and were picked up by a passing police unit.

"Mum was rather worn-out and exhausted and the young fellow was surprisingly good."

The two were taken to Singleton Hospital with dehydration and insect bites but were otherwise uninjured.

Michelle Pittman and her son Dylan went missing in the Mount Royal National Park in NSW (Google Maps).

Michelle Pittman and her son Dylan were found along Mount Royal Road within the Mount Royal National Park (Google Maps).

Acting Supt Post said he has visited them in hospital today.

"Young Dylan was in good shape," he said. "He has lots of insect bites that are annoying him and he was quite hungry.

"Mum was quite weak and I imagine she'll take more time to recover."

The mother and son survived 10-days in the bush thanks to survival skills learned from Bear Grylls (Photo by: Ben Simms/NBC/NBCU Phhoto Bank).

He said Ms Pittman was aware of her condition throughout the 10 days, and made reference to Bear Grylls’ survival skills after being rescued.

"They managed to get hold of water by licking water off plants and digging water from holes and using leaves to collect it," Acting Supt Post said.

"They didn't eat anything the whole time."

Acting Supt Post confirmed Dylan lost his shoes during the ordeal but said he was "the real hero".

"I'm sure they helped each other. As she got weaker, he helped maintain her focus," he said.

A large-scale search involving police, SES, NSW Ambulance paramedics and National Parks and Wildlife had been trying to find the two since their car was found parked at the park on Monday, October 9.

"They didn't tell anyone where they were going but they had a note, a wish list of places they wanted to go to during the school holidays," Acting Supt Post said.

"It included state forest all the way up the Barrington Tops, it gave us quite a large area to clear."

Acting Supt Post said Ms Pittman was "trying to entertain" her son during the holidays and had "designed a bit of an itinerary" of outdoor activities.

It's believed the mother and son had only set out for a short walk within the park – which is 187km north of Sydney – before becoming lost.

"It is unbelievable how thick the rain forest area is, if you move away from the main walking tracks it'd be very easy to get lost," he said, explaining Ms Pittman and her son simply got "disorientated".

The weather also complicated the search.

"There was heavy fog on Tuesday," he said.

"We had aircraft organised to help us in the search but they were unable to participate due to the fog and the walkers on the ground were also limited by it."