Police searching for a missing student in Sydney say they believe he may have been killed by his suspected kidnappers.

Jamie Gao, 20, was last seen getting into a white car on Arab Road in Padstow in Sydney's south-west last Tuesday afternoon.

The vehicle had been parked near a fast food restaurant and left shortly afterwards.

Witnesses have told detectives the Hurstville student was talking to two men, who have been described as being of Asian appearance.

Mr Gao's own car was later found abandoned in Padstow.

Police say they have been told the 20-year-old was excited about the arranged meeting and his disappearance and lack of contact are out of character.

Robbery and Serious Crime Squad commander Detective Superintendent Luke Moore said personal items were in Mr Gao's car which was discovered nearby.

"The circumstances in which he went missing lead us to believe that it is possible that he met with foul play," Detective Superintendent Moore said.

"Mr Gao's car was located a short distance away and there was some personal items which were located near the scene.

"It's possible that Mr Gao was getting himself into some kind of trouble and indeed may have been getting in over his head."

Police say Mr Gao is about 170-175 centimetres tall and has black hair and brown eyes.

Anyone with information on the disappearance is encouraged to call Crime Stoppers on 1800 333 000.