Ms Moore and her mother, Noelene Campbell, were accompanied by the Orana Mid-Western Police District Commander, superintendent Danny Sullivan make an emphatic plea for anyone to help them locate David Campbell who has been missing since March 14 this year.

It's been 17 weeks since Ms Moore said they last heard from Mr Campbell, Ms Moore's sibling who turned 42 on May 23, and who has no idea he has two relatives who passed away and their mother is due for hospital operation soon.

"We're desperate to know how he is, not much about where he is, but more that he is safe. He didn't take his car, he didn't take his bank card. There's been no activity on his phone. We don't know if he has money or something to eat.

"If he is hitchhiking now that the weather is getting cold, we don't know if he is warm...not knowing anything is just really, really hard."

Superintendent Sullivan said they are appealing for the public to provide police with "any piece of information that can help us put this puzzle together...we just want to make sure that David is safe.

"The key piece is to tell us he is safe, he doesn't have to tell where he is or who he's with."

As the investigation into Mr Campbell's disappearance is now running 17 weeks, superintendent Sullivan said police are "not ruling out anything in or out about David's disappearance" and "will leave no stone unturned".

"The key for us is working with his family, they're human beings and they have questions that need to be answered...We'll make sure that this investigation is the best it can be to determine where David is."

Mr Campbell, whose latest photo was shown by Ms Moore, was last seen about 8 pm on Monday, March 14 this year at a home in Bunglegumbie Road, Dubbo.

Police said Mr Campbell is known to frequently travel to Central Coast, Orange, Nyngan, and Alice Springs in the Northern Territory.

Last month, police renewed calls for public assistance in locating Mr Campbell who has been missing since March but initial investigations are not indicating anything about his whereabouts.

Officers began investigating his whereabouts on March 14 this year when his family first reported him missing.

Mr Campbell is described as being of Caucasian appearance, approximately 182cm tall, of large build, light brown hair, and stubble. It is not known what he was wearing at the time he went missing.

Anyone with information regarding Mr Campbell's whereabouts is urged to contact Dubbo Police Station on 6883 1599 or Crime Stoppers on 1800 333 000 or https://nsw.crimestoppers.com.au.