This study on the relationship between a childhood maltreatment and later criminality for adolescents diagnosed with attention deficit/hyperactivity disorder (ADHD) found that the presence of moderate to severe childhood maltreatment increased the risk of later arrest more than the risk associated with childhood early conduct disorder (CD). In addition, the study found that the presence of both childhood maltreatment and childhood CD significantly increased the risk of recidivism for adolescent/young adults. The primary objective of this study was to investigate the effect that moderate to severe childhood maltreatment had on later criminality for young adults/adolescents diagnosed with ADHD. Data for the study were obtained from a sample of 88 adolescents diagnosed with ADHD and screened for comorbid disorders at age 7 through 11. The adolescents were evaluated at the 10-year follow-up to determine the extent to which their criminal history, or lack of, was influenced by the presence of a history of childhood maltreatment. The findings from the study indicate that the presence of childhood maltreatment is a risk factor for later criminality in youth diagnosed with ADHD, and that this risk factor is independent of contributions from childhood early CD. These findings suggest the need for children with ADHD to be screened for childhood maltreatment in order to identify those at increased risk for criminal activity later in life. Implications for research, policy, and practice are discussed. Tables and references