We studied the duration of migraine attacks among children and adolescents who reported headache attacks lasting <2 h. Among the 720 children who attended our specialist headache clinic, over a period of 6 years, 231 children had migraine with or without aura fulfilling the International Headache Society (IHS) criteria for the diagnosis of migraine. A further 15 children reported headache attacks typical of migraine, but of duration <2 h. They were asked to fill prospective headache diaries in order to determine with accuracy the duration of their headache attacks. Ten (67%) of these children provided prospective fully analysable headache diaries and recorded a total of 120 headache attacks, 66 attacks (55%) lasting for <1 h each, 30 attacks (25%) lasting between 1 and 2 h, and 24 attacks (20%) lasting >2 h. Patient-based analysis of the headache diaries showed that only three children consistently had headache attacks lasting <1 h. Seven children had some of their headache attacks lasting for at least 1 h and four had some of their headache attacks lasting at least 2 h. This study shows that headache attacks in children with migraine can be variable, and brief attacks are rare. A combination of short (<1 h) and long (>2 h) attacks of headache can coexist in the same patient. The IHS diagnostic criteria of 1988 for migraine in children should therefore acknowledge such variation and allow reduction of the duration of migraine attacks to 1 h.