Two men were airlifted to hospital from Gulargambone after a quad bike hit a tree on New Year's Day.

Emergency crews were called to a dirt track near the local racecourse at around 7pm, where they found an 18-year-old and 28-year-old had been flung from the vehicle while heading towards the Castlereagh River.

Both men were treated for head and leg injuries, while the NSW Ambulance media unit said the 28-year-old had possible pelvic injuries and was in a serious condition.

Two helicopters landed in a nearby paddock before one took the the 28-year-old to Westmead Hospital in Sydney.

The other took the 18-year-old to Tamworth.

Three ambulances, police and a Rural Fire Service (RFS) crew were on site, while police and SES crews stayed until roughly 1:30am before the quad bike was towed.

Police also inspected the scene and took photos.