Nigel Peterson's family optimistic of finding him

Missing man Nigel Peterson.

The family of missing Rotorua man Nigel Peterson remain "optimistic and hopeful" of finding him, nearly four weeks since he was last seen.

Rotorua police are still appealing for sightings of Peterson, 33, who has not been seen since November 17.

The last sighting of Peterson, who is autistic, was around 3pm that day on Old Taupo Road when he walked off from the caregiver he was with.

In a statement, police said his family remained optimistic and hopeful of finding Peterson and police wanted to hear from anyone who believes they may have seen him since November 17.

"We'd like to thank everyone who has contacted police to date – we are following up all credible information received," the statement said.

If you can help, please call Rotorua police on (07) 349 9139 and quote file number 171117/2007.