Four people have died after two cars and a semi-trailer collided on the Great Western Highway in western NSW.

Emergency services were called to Glanmire, east of Bathurst, about 1.40pm (local time) on Saturday following the three vehicle accident.

The three occupants of one of the cars died at the scene, while a passenger in the other car was also killed.

The driver of the second car was injured and is in a critical condition.

The truck driver was not injured.

-AAP