Hematomata are well-recognized complications of surgery. Subperiosteal hematomata occur rarely and have not been well documented after craniofacial surgery. It is possible that craniofacial surgery increases the likelihood of subperiosteal hematomata occurring after minor trauma, even long after surgery, with a risk of subsequent ossification. Over a period of 7 years, 12 patients were identified as having possible subperiosteal hematomata. A number of these patients displayed distinct ossification in the area of the subperiosteal hematoma, resulting in an obvious contour defect. This can be prevented if the patients present early enough and if the hematoma is evacuated. Prompt evacuation of the hematoma is therefore suggested in any case with a history suggestive of a subperiosteal hematoma.