A Sydney teenager's online petition has prompted the New South Wales Government to cut the cost of car parking at public hospitals by about $200 a week.

Fourteen-year-old Gidon Goodman, who has a rare blood disorder and has to go to hospital for regular medical infusions, started the petition because he was concerned family members would stop visiting their sick relatives due to high hospital parking costs.

Today, Premier Gladys Berejiklian responded to his campaign, which garnered more than 70,000 signatures, by announcing "a huge reduction in car parking fees" at all New South Wales hospitals.

"Instead of paying about $200 a week, they'll be paying about $20 a week," she said.

"Some families will be saving hundreds and hundreds of dollars every month."

The Premier (right) praised Gidon for making a difference to people's lives. ( ABC News: Stephanie Dalzell )

The Premier said affected car park operators would get $11 million a year in compensation as a result of the fees being slashed.

"It does mean negotiating, it also means as a government we have to do what's called forego revenue," she said.

"So we're talking millions and millions of dollars.

"We will be contributing to this every year."

Ms Berejiklian praised Gidon's efforts in advocating for the change and pressing the Government.

"Today is about people making a difference ... a teenager like Gidon making a difference," she said.

"This is a huge boost for families patients and for carers who are visiting all of our public hospital

Gidon said he was thankful the Government had acted to make it easier for families and carers to visit sick patients.

"I'm now unbelievably proud to be able to say that the Premier and the Health Minister are introducing a policy which is going to do amazing things for the families," he said.

"Someone [visiting] once a week for a year will be saving $1,600.

"These changes are going to be helping people who go [regularly visit hospitals] long term, helping families, people having babies [who] have to go longer than two days in a row."

Health Minister Brad Hazzard said Gidon's campaign had sparked a review into the costs of car parking.

"As soon as I became Health Minister, I met with Gidon, I listened to his concerns and I agreed. Gladys Berejiklian and I determined that we would move as quickly as possible and we have," the Minister said.

"He brought it to the Government's attention."

Gidon said trips by his family to visit him in hospital had cost them thousands of dollars in car parking fees.

The parking fee changes come into effect from July 1.