A man had to be cut free from an overturned car after a head-on collision in Buckshaw Village.
Firefighters had to cut the roof off the man's car to rescue him, before he was taken by ambulance to Royal Preston Hospital.
North West Ambulance Service dispatched two rapid response units to the scene and confirmed that the man suffered serious injuries.
The crash happened in Townsend Drive, near the Tesco Superstore in Buckshaw Village at 9.20pm on Tuesday November 20.
An 18-year-old man, from Leyland, was arrested on suspicion of drug driving. But police could not confirm whether he was also the injured party.
The driver of the other vehicle, a woman in her 20s, was not seriously injured.
A police spokesman said: "We were called at 9.23pm on November 20 to reports of a two vehicle collision on Townsend Drive, Buckshaw Village.
"The road was closed while emergency services attended.
"An 18-year-old man from Leyland was arrested on suspicion of drug driving.
"He has been released under investigation."
Two fire crews from Chorley had to rescue the injured man from the vehicle using specialist cutting equipment. Firefighters had to use stabilising equipment to prevent the vehicle moving whilst the man was freed from the wreckage.
A spokesman for Lancashire Fire and Rescue Service said: "Two fire engines from Chorley attended a road traffic collision involving two vehicles on Townsend Drive in Buckshaw Village.
"One casualty was rescued from a vehicle by firefighters who used cutting equipment, stabilising equipment and a longboard.
"The casualty was taken to hospital by paramedics."