The relationship between seatbelt use and injury severity, brain lesion location, and functional outcome was investigated in 163 individuals who sustained traumatic brain injuries in motor vehicle collisions. Of this group, 31 were using a seatbelt at the time of the accident and 132 were not. Restrained motor vehicle occupants were significantly more likely to sustain damage to subcortical brain structures than unrestrained occupants. Conversely, unrestrained occupants sustained a greater frequency of posterior brain lesions. In addition, demographic and behavioral variables were significantly related to increased likelihood of seatbelt use. Analyses revealed no significant differences between groups for injury severity variables and functional outcome measures. Seatbelts alter the body's response to forces applied in motor vehicle collisions, creating disparities in lesion sites between restrained and unrestrained motor vehicle occupants. The relationship between seatbelt use and injury severity and functional outcome is discussed.