Background: Headache and sleep are related in different ways and alterations of chronobiological mechanisms are involved in headache. We investigated the relationships between headache and sleep quality in a large non-clinical population of children and adolescents and evaluated the relationship between headache and circadian typologies. Methods: A total of 1073 children and adolescents (50.9% males; mean age = 10.56; range = 8À15 years) were recruited from four schools in Rome. They filled out the questionnaires individually in classrooms, after brief group instruction about answer for-mats. The questionnaires included (a) a self-report headache questionnaire to collect information on different aspects of headache attacks based on the International Classification of Headache Disorders-2nd edition (ICHD-2); (b) the School Sleep Habits Survey that incorporated questions about sleep habits, the Sleep–Wake Problems Behaviour Scale (SWPBS), the Sleepiness Scale (SLS) and the Morningness/Eveningness Questionnaire (MEQ). Results: According to ICHD-2 criteria, we classified 70 (6.5%) children as Migraine Group (MG), 135 (12.7%) as Non-Migraine Headache Group (NMG), and the remaining 868 (80.8%) were classified as Headache-Free Group (HFG). No clear differences have been found between MG and NMG regarding the frequency of the attacks, although MG showed a significantly increased frequency of long-lasting attacks. The modality of onset of pain and the location of pain was similar in both groups. The most frequent trig-gering factor for headache in MG and NMG was ''a bad sleep'' (32.2%) followed by emotional distress (27.8%). No differences have been found between MG, NMG and HFG in sleep schedule or sleep duration. MG and NMG showed significantly higher scores on the SWPBS vs. HFG, while MG presented higher scores on the SLS compared to NMG and HFG. MG presented lower MEQ scores, indicating a more pronounced eveningness. Conclusions: The relationships between headache and sleep problems are evident even in a non-clinical population of children and adolescents, with MG showing poorer sleep quality, sleepiness and a tendency toward eveningness. Ó 2007 Elsevier B.V. All rights reserved.