Sussex Police has released CCTV of a collision which left a child with serious head injuries on Sunday (September 16).
A nine-year-old boy was on a scooter in Whitehawk Road at 12.15pm, when the collision with the moped took place.
Police said the rider of the moped, who had a passenger and was travelling south, failed to stop at the scene.
A police spokesperson added: "The vehicle, which is believed to be stolen, is described as silver and black or dark red, and is suspected to have some damage as a result of the impact."
The boy was taken to Royal Sussex County Hospital with serious head injuries, police said, and he has since been discharged.
Anyone with any information about the collision is asked to report it online or call 101, quoting serial 502 of 16/09.