There is a growing body of research supporting the existence of deficits in brain anatomy associated with ADHD, with evidence of reductions in overall brain size, cortical gray matter and subcortical structures. However, reported effect sizes are small and results not always consistent. Anatomical MRI studies may be easily confounded, as brain development is complex and associated with both progressive and regressive changes in brain anatomy. In this study, we propose to combine longitudinal data from a large cohort of children and adolescents with state-of-the-art imaging methods (including diffusion tensor imaging and voxelbased morphometry) to investigate brain development in ADHD. This will allow us to address the question whether ADHD represents a disruption or a delay of brain development.