A Tasmanian man says his son's happy nature inspired him to carry the boy who has a disability for a week-long bushwalk on the Overland Track.

Eight-year-old Jack Duffy has cerebral palsy and cannot walk, talk or eat on his own.

Most people who walk the Overland Track take a backpack that weighs between 13 and 20 kilograms.

But Jack's father Chris Duffy's backpack was specially designed to carry his son Jack, who weighs 37 kilograms.

Mr Duffy said the highlight of the walk was a rest stop at one of the mountain passes.

"I was sitting there looking at Jack and sort of got a little emotional thinking that he was probably the first non-abled body, little boy or person maybe to be in that spot," he said.

The gruelling bushwalk would not have been possible without the support of 13 friends who carried extra gear like nappies and specialised feeding equipment for Jack.

Lauren Atkinson, a real estate agent in Launceston, decided to volunteer as one of Mr Duffys' support crew.

"I don't think anyone can really appreciate how difficult it is to carry 37 kilos of wriggling child on your back, but Chris is a gun, Chris is amazing," she said.

Chris and Erin Duffy with eight-year-old Jack: "His smile, it sucks people in, just his attitude to life." ( Supplied )

"He just did it. There were some quite treacherous parts of the walk and he just did it and Jack loved it, every second."

Mr Duffy said he knew his son was having a good time.

"He's got amazing expression, he doesn't miss a thing, he's a cheeky little rat, really," he said.

"His smile, it sucks people in, just his attitude to life."

Jack's mother Erin was also on the trip, putting extra layers on her son at times to make sure he stayed warm when it started snowing.

She said it was obvious how much Jack enjoyed the six-day walk.

"Being out in the wilderness with his dad and just having fun, it was just so much fun and it was just really rewarding to see him so happy," she said.

It is not the first time Mr Duffy has been on an adventure with his son in Tasmania.

In 2009 he kayaked with Jack from Launceston around the East Coast to Hobart, raising $70,000 for a local disability support centre St Giles.

This time the Duffys have raised $20,000 for the disability support provider Life Without Barriers.

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"We got the inspiration through Jack because he's such an inspirational little man," he said.

"He's got so many reasons not to be happy, content with his own life, because of challenges he faces, but he's so happy and loving and inspires us every day to do these things."

Ms Duffy said there were children who did not have the same support as her son and he wanted to raise money to help them.

"We'd like to do something that involves more people and lets more kids like Jack get involved," she said.

"And we're considering trying to get a bunch of kids to do a triathlon together, with support crews for each of those individual children."