Friends of three young Sydney men killed in an horrific crash in the Blue Mountains yesterday have gathered to remember their mates.

Lachlan Burleigh, 17, Ben Sawyer, 19, and Luke Shanahan, 21, all died at the scene when the Mitsubishi 4WD they were passengers in collided head-on with a Subaru Impreza on Bells Line of Road at Bilpin at about 3.30pm yesterday.

Their 20-year-old P-plate driver, a front seat passenger and an elderly pair in the Subaru were pulled alive from the crash and transferred to Westmead Hospital.

All are expected to make a full recovery.

Lachlan Burleigh, 17, was due to graduate from high school in the coming weeks. (Supplied)

Luke Shanahan, 21. (Supplied)

Ben Sawyer, 19. (Supplied)

The group had been travelling back from a music festival in the region to their homes on Sydney’s northern beaches.

Friends said Lachlan was just weeks away from graduating from high school Oxford Falls Grammar, where flags flew at half mast today.

He had attended the school since kindergarten and both his mother and aunt are staff members.

Loved ones met near the Warriewood local’s favourite Turimetta Beach today and said Lachlan hoped to become a marine biologist after school.

"Lachlan, I’m telling you, was one of those guys who just brought light into the world,” friend Warren Peters told 9NEWS.

"He was never, ever rude, never mean.

"Just a really good bloke."

The trio had been returning from a a music festival when they were involved in a head-on crash. (Supplied)

Mr Sawyer's aunt Wendy said the entire local community was reeling after the loss of three popular young men.

"We are devastated beyond belief," Mrs Sawyer said in a statement.

"Devastated, not just for our boy but for everyone involved.

"All the boys are victims of this tragedy.

"It's rocked the entire community."

It is the second tragedy to hit the family after Mr Sawyer's older brother Nathan passed away aged just 17 in 2010.

"Youre family's going to miss you Benny," family friend Tom Leach said.

"At least you're with Nathan now."