The level of agreement between different sources of information, i.e. questionnaires, interviews and diaries, was evaluated in a sample of 129 schoolchildren, 69 girls and 60 boys, ranging in age from 7 to 17 years. Headache diagnoses and headache features showed high agreement between questionnaires and subsequent interviews. The concordance between questionnaires and interviews for headache diagnoses increased, and the number of unclassified headaches decreased, when the International Headache Society (IHS) duration criterion was excluded. When comparing headache frequency reported in questionnaires and interviews with diary recordings, the agreement was low and the frequency higher in the diaries. Overall, the agreement between questionnaires, interviews and diaries was not related to age or gender. The questionnaire may serve as a valid source of information in studies of headache in schoolchildren. Prospective recordings in diaries provide additional information, in particular of low-intensity headache. In children, the IHS duration criterion should be modified or excluded.