Cancer patients in the Northern Territory should have access to a long-awaited PET scanner in May 2018, eight years after it was first promised by politicians.

Territorians suffering cancer should finally get access to a PET scanner by May 2018, eight years after it was first promised.

The deadline was set for the positron emission tomography (PET), which detects and tracks cancer, after funding was fast-tracked.

The federal government will chip in $15 million for the device while the NT government will pay an additional $5 million.

It was first pledged during the 2010 federal election by then shadow health minister Julie Bishop and then-candidate for Solomon Natasha Griggs.

Ms Griggs re-promised the scanner during the 2016 federal election, where she lost her seat to Labor's Luke Gosling, who also promised to deliver the scanner if elected.

The NT is the only jurisdiction without one, forcing cancer patients to travel interstate for diagnosis.

"Locals should be able to receive this type of medical treatment in Darwin rather than travel," NT Health Minister Natasha Fyles said.

"There has been a lot of talk about this project - even some scepticism about whether it would happen - but this $5 million in fast-tracked funding shows we are actually making it happen."

The NT government also announced $12 million in funding for a multi-storey car park at the Royal Darwin Hospital.