There is considerable evidence that attention deficit/hyperactivity disorder (ADHD) is associated with conduct problems, social maladaptation and delinquent behavior. The "Ottweiler Study" was performed to elaborate the prevalence of ADHD and comorbid disorders in 129 young adult detainees of the juvenile prison of Ottweiler (Germany) according to DSM-IV and ICD-10 criteria. Here we report psychopathological characteristics of 28 inmates, who fulfilled the diagnostic criteria for persisting ADHD, and 37 individuals with neither a history nor current ADHD symptoms. Childhood ADHD symptoms but no current ADHD were present in 64 individuals. The Wender-Reimherr Interview (WRI) based on the Utah criteria for adult ADHD, the NEO-five factor personality inventory (NEO-FFI) and the youth self report/young adult self report (YSR/YASR) according to Achenbach were used for the assessment of psychopathology and the description of behavioral problems. Regarding WRI and YSR/YASR we found a significant increase of emotional and internalizing problems in the ADHD group compared to delinquents without ADHD or ADHD history. ADHD delinquents scored higher on the personality dimension neuroticism, and showed lower scores on the dimensions agreeableness and consciousness. Using discriminant analysis, high scores on the WRI subscales disorganization and attention difficulties and NEO-FFI neuroticism were the best predictors of ADHD diagnosis. The results support prior findings of high ADHD prevalence in prison inmates and suggest that emotional and internalizing abnormalities are prominent problems in this population. Further studies are needed to elucidate the role of ADHD as an independent factor for life-persistent criminality, since specific treatment may help to ameliorate the legal prognosis.