A man has died after being crushed against a wall by a car in Sydney's north.

Emergency services were called to Paul Close, Hornsby Heights, about 8pm, after reports a man attempted to stop an unattended car from rolling down a hill.

On arrival, police found an 18-year-old man trapped between a wall and the car.

He was released from between them a short time later, but despite the efforts of paramedics, he died at the scene.

Officers from Kuring-Gai police area command attended and established a crime scene.

An investigation is underway to determine the circumstances surrounding the crash.

A brief will be prepared for the Coroner.