Two thirds of all felons released from state prisons are rearrested within 3 years. This appalling recidivism rate explains the intense and growing interest on the topic of desistance from crime. Yet, inexplicably, one of the major factors affecting desistance from crime and the recidivism rate has received scant attention. That factor is attention-deficit/hyperactivity disorder (ADHD). This article establishes the widespread prevalence of ADHD in the prison system and the critical importance of identifying and treating ADHD as an essential component for any best practice models for preventing crime and reducing recidivism. It also examines the major mechanisms whereby ADHD increases the risk for crime and recidivism.