A land, sea and air search is underway for missing backpacker Theo Hayez who was last seen leaving a Byron Bay bar more than a week ago.

Key points: Theo Hayez was last seen leaving Cheeky Monkey's bar in Byron Bay alone

Theo Hayez was last seen leaving Cheeky Monkey's bar in Byron Bay alone Friends and family say he was looking forward to returning to Belgium in the coming days

Friends and family say he was looking forward to returning to Belgium in the coming days Fellow backpackers and local residents have been conducting their own searches

The 18-year-old Belgian national failed to check out of the WakeUp! Backpacker hostel on Thursday, leaving all his belongings untouched, which prompted hostel staff to report him missing.

He was last seen leaving the Cheeky Monkey's bar about 11:00pm on May 31, wearing a black hooded jumper, beige pants and black shoes.

On Sunday, police conducted a major search in the Byron Bay area with the assistance of rescue officers, the State Emergency Service, a lifesaver helicopter and lifesavers with marine vessels.

The most recent photo of Theo Hayez which he sent to his family. ( Supplied: Facebook )

Mr Hayez's cousin, Lisa Hayez, has also pulled together her own search party with the help of fellow backpackers and locals wanting to help.

She said they had been checking bushland and nearby beaches.

"We are just walking and checking everywhere to see if we can find him," she said.

"We're going to keep going for as long as we need to … people can come and join."

Ms Hayez said her cousin was a very positive, happy young man who kept in touch with his friends and family regularly.

He was due to fly home to Belgium on June 12.

"He had no reason to do this … he was really excited to go home," Ms Hayez said.

Ms Hayez said she had received many calls from across the country with people claiming to have seen Mr Hayez.

"But really, a tall guy with long blonde hair could be everywhere," she said.

NSW Police told the ABC they were unable to provide an interview.