Attention-deficit hyperactivity disorder (ADHD) in adults has been associated to a higher probability of problems with justice. Studies in prison populations disclosed higher prevalence of this disturbance. ADHD association with personality disorders and higher substance abuse could partially help in the explanation of this phenomenon. Based in a literature review, the authors present a reflection on the possible implications of the ADHD diagnosis to Forensic Medicine. After a brief review of the clinical aspects, epidemiology, etiology and nosology of ADHD, its repercussions in the sphere of justice are analysed, namely the prevalence of associated criminality, risk factors and the co-morbidity with personality disorders and substance abuse. These elements are used as a base to the discussion of the results and to a subsequent reflection on the question of (in)imputability related with this disorder.