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.