BackgroundHigh intelligence may be associated with positive (adaptive, desired) outcomes, but may also come with disadvantages.AimsTo contribute empirically to the debate concerning whether a trade-off in IQ scores exists in relation to attention-deficit hyperactivity disorder (ADHD) and related problems, suggesting that high intelligence – like low intelligence –increases the risk of ADHD.MethodCurves of the relation between IQ score and ADHD problems were fitted to questionnaire data (parent, teacher, self-report) in a population-based study of 2221 children and adolescents aged 10–12 years. Externalising and internalising problems were included for comparison purposes.ResultsHigher IQ score was most strongly related to fewer attention problems, with more rater discrepancy in the high v. average IQ range. Attention problems – but only minimally hyperactivity/impulsivity problems – predicted functional impairment at school, also in the higher IQ range.ConclusionsAttention problems in highly intelligent children are exceptional and affect school performance; they are therefore a reason for clinical concern.