A teenage boy is fighting for life after allegedly being kicked in the head and knocked unconscious outside a fast-food restaurant north of Brisbane.

The 17-year-old had finished a heated argument with another teenager outside the Redcliffe McDonald's on Friday night when he was struck by an 18-year-old man, police allege.

He fell back and hit his head on the bitumen.

The 17-year-old suffered head injuries and is in hospital in a critical condition. (9NEWS)

Police want to speak to a witness who provided first aid to the boy. (9NEWS)

The boy is in a critical condition at Royal Brisbane Hospital.

"He was put in an induced coma at the scene," Queensland Ambulance operations supervisor Brad Hardy said.

The 18-year-old has been charged with one count of grievous bodily harm and will appear in Redcliffe Magistrates Court on Monday.

The 18-year-old man has been charged with one count of grievous bodily harm. (9NEWS)

While it was initially labelled a one-punch attack, police allege the accused delivered a single kick to the victim's face after his friend exchanged heated words.

Mr Hardy said it was "terrible to see a young life potentially destroyed" in such a manner.

Police want to speak to a witness who provided first aid to the boy and are appealing for any dashcam footage from motorists.