We applied the second edition of the International Classification of Headache Disorders (ICHD-II) in 417 children (age range, 2–12 years) with chronic headaches attending a pediatric headache clinic. The initial diagnosis was made according to the ICHD-II while the final diagnosis was, based on the longitudinal intuitive clinical diagnosis (LICD), deemed to be the gold standard. The diagnosis of migraine without aura had a sensitivity of 52%, a specificity of 100% and a positive predictive value of 100%; for the diagnosis of migraine (at the one-digit level) these values were 87%, 100% and 100%, respectively. The ICHD-II criteria for migraine without aura have high specificity but low sensitivity in childhood, even considering the minimal duration of the attacks to be 1 hour. Other factors, such as the existence of subgroup 2.4 (probable tension-type headache), are responsible for the low sensitivity of ICHD-II criteria for the diagnosis of migraine without aura in patients of this age group.