Last Tuesday, police visited Glen Waverley car parks to observe motorists' awareness of potential theft from cars.

While many had heeded the safety call, a large number of cars were found to have satellite navigation devices, laptops, CDs and other valuables in clear view of prowling thieves.

Other items that frequently attract opportunistic thieves include GPS suction cup holders, mobile phones, loose change, wallets and handbags.

Glen Waverley police's Sergeant Rod Moroney was not surprised at the results of the operation, saying theft of valuables from cars was a "constant" problem in Monash.

"People often forget to put things away or think it won't happen to them.

"We try to tackle the problem with regular operations where we walk through car parks, looking for things in cars and notify drivers with letters."

When last week's operation began, Constable Mick Allen immediately noticed a laptop on the front passenger seat of a van. He said it was a "classic" item left on passenger seats.

"People think no one would be willing to go to the extent of breaking a window but it barely takes a second for it to happen."

The owner of the van returned to his car while Constable Allen was speaking to the Journal.

The Donvale resident said he simply forgot to put it under his chair.

"I will definitely remember to do it now," he said.

Most had only one valuable left behind but during the patrol, a car was spotted with many items in plain view including a suction cup holder, a switched on GPS device, loose change, a handbag and a sports bag.

Constable Danielle Scorer said a common misconception occurred where people believed an empty suction cup holder was not attractive to thieves.

"Just because it's left without the system doesn't mean they won't try to break in. They can often think the GPS will be hiding in the glove compartment.

"People need to be aware of the mark left when removing a suction cup holder from the windscreen. It is a dead giveaway. That's why we have wipes available at stations which clear away the ring."

More than 52,000 thefts from cars were recorded in Victoria during the 2007-08 financial year.