The onset of post-traumatic headache occurs frequently in children, where it is often caused by severe head injuries, therefore, it is part of a post-traumatic syndrome, rather than of an independent headache and in this case no cause is clearly evident. The problem, conversely, arises in post-traumatic headache after a light trauma, since it is difficult to establish the cause-effect link. We have studied PTH incidence for one year in the patients of the emergency ward of the Saint Charles of Nancy Hospital, compared to the activity of 4 Italian headache centres. At the Saint Charles of Nancy Hospital of 98 patients with PTH after a moderate head trauma, 18 had acute and 26 chronic PTH, the majority ceased after six months. In the Italian headache centres 1,656 patients were examined, of these 3.2% suffered from PTH: 25 acute, 29 chronic. These data confirm the poor evidence of PTH after a light trauma and lead to doubt of the existence of this nosological entity.