The seriously injured boy remains in the hospital for surgery, Region Östergötland states.
He is a resident of Norrköping.
It was just before 11 o'clock that the traffic accident happened between the moped and a car happened at Gäddestad, east of Östra Husby.
Police, rescue services and an ambulance were alerted to the scene and a total of three people must have been involved.
The moped driver, the 15-year-old boy, was taken to hospital by ambulance.
- We will investigate the cause of the accident and have prepared a report regarding traffic offenses, says police spokesperson Monica Bergström.