Children involved in high-speed vehicle collision could be particularly exposed to severe injuries when adult restraints are used. We report a case where adult 3-point restraint used without booster seat was responsible for severe thoracic injury resulting in complete shoulder and clavicle dislocation, occipito-atloidal dislocation, and complete disruption of right common carotid artery in a 7-year-old boy. Misplacement of the adult shoulder harness at the base of the neck could be directly responsible for these lethal injuries, which could probably be avoided by concomitant use of a booster seat.