Moving house is never fun, especially when you reach the dreaded bond clean stage — unless, that is, you stumble across a stash of diamonds in the process.

The thorough cleaning practices of a Cairns renter have uncovered a haul of diamonds that police believe may have been hidden for more than a decade.

Senior Constable Russel Parker said it was believed that at some point from about the year 2000 somebody had "left this little stash secreted inside the unit".

"It was only found because [the property] was undergoing such a thorough clean," he said.

Senior Constable Parker said police were trying to reunite the diamonds with their rightful owner, but were remaining tight-lipped about the exact details of the find.

He said fewer than six diamonds were found, but would not say how big they were, or how much they were worth.

"We're not going to describe the stones or anything like that but anyone who's left diamonds behind in a residence, I'd suggest, would remember," he said.

"We've made enquiries with jewellers and so on to see if there's any way of tracing the owners and there doesn't appear to be.

"These are quality diamonds and certainly they represent quite a deal of money."

Authorities are unsure whether the stones were legitimately owned and innocently stashed, or if something more nefarious is at play.

"It could be that they were the proceeds of a crime, but with the identifying documentation [the stones were found with], they haven't been reported stolen," Senior Constable Parker said.

Cleaning is a tenant's best friend

Senior Constable Parker said regardless of the origin of the stones, the "impeccable honesty" of the person who found them deserved praise, and potentially something more.

"The first thing the tenant did was to realise that 'Well look, I don't own these things', so they came down to the police station and handed them in.

"And there is a very, very good chance that the tenant will end up with these stones again if we can't find the rightful owner of them."

Lost property is generally held by Queensland Police for about two months before the person who found it gets to keep it.

But because the stones are so valuable, police have extended the timeframe in a last-ditch effort to locate the rightful owner.