Police said the man, 34, was struck by a four-wheel-drive on Parramatta Road in Croydon about 10.15pm on Monday.

It will be alleged the driver failed to stop and fled.

A witness gave police information about the vehicle involved, leading officers to stop a car in nearby Auburn.

A driver was arrested and taken to Auburn Hospital for mandatory tests.

The pedestrian remains in Royal Prince Alfred Hospital in a critical condition.

Police are also appealing for information following a hit-and-run in Campsie last week.

A 68-year-old woman was crossing Ninth Avenue on the pedestrian crossing when she was hit by a car on September 24 about 6.30am.

The driver failed to stop.

The victim was taken to Canterbury Hospital where scans revealed she had sustained a fractured and dislocated shoulder.

Investigators have been unable to identify the type of vehicle.

Detective Inspector Paul Albury from Campsie Local Area Command said he was disappointed to see a motorist fail to stop after being involved in a collision.

"To drive off and leave a woman lying on the road with serious injuries is not only disappointing but also a cowardly act," he said.

"This is someone's mother who has been seriously injured and now faces months of specialist medical treatment and possible surgery.

"I would urge the driver involved to have a conscience, take some responsibility for their actions and hand themselves in to police.

"We would also like to hear from anyone who witnessed the collision and can provide any information that would help us solve the case," he said.

Anyone with information is asked to contact Crime Stoppers on 1800 333 000.

Fairfax Media