NSW cops arrest alleged one-punch attacker

A man has been arrested over a horrific and unprovoked one-punch attack on a teenager in Sydney's CBD last month.

The 18-year-old victim was walking with a friend on Park Street at about 2.30am on November 23 when he was hit from behind and knocked unconscious before he'd even hit the ground.

CCTV footage of the attack captured the male running at the victim and then striking him in the head.

A police manhunt for the alleged attacker ended on Friday, with a 22-year-old man arrested at a hotel on George Street about 5pm.

The man was taken to Day Street Police Station where he is expected to be charged.

In an earlier appeal for the alleged attacker to hand himself into Superintendent Gavin Wood described the incident as "nothing short of horrific".

"We have an innocent, 18-year-old man who has been hit by a coward. It's not only a horrendous act in terms of what he's done, it's a cowardly act," he said.

"It's one of the worst things I've seen."