Aims: To investigate the onset and outcome of alcohol dependence in subjects with childhood attention deficit/hyperactivity disorder (ADHD) in a Turkish sample. Methods: Among patients being treated for alcohol dependence, 15 had a history of childhood ADHD [ADHD (+)] and 45 did not [ADHD (-)]. ADHD history was assessed according to DSM-IV criteria by a child and adolescent psychiatrist who interviewed the subjects and their close relatives. Severity of dependence was measured by the Michigan Alcoholism Screening Test. Subjects were followed up for 1 year for the assessment of relapse. Results: The age of onset for alcohol drinking, alcohol abuse and alcohol dependence were significantly lower in the ADHD (+) group than in the ADHD (-) group. Comorbid substance use was more prevalent in the ADHD (+) group. The study found no significant difference in the severity of alcohol dependence between ADHD (+) and ADHD (-) groups. During follow-up, 80% of the ADHD (+) subjects relapsed, compared with 55.6% in the ADHD (-) group. Relapse occurred on average 2.74 months earlier in the ADHD (+) group than in the ADHD (-) group. Conclusions: As found in other countries, alcohol dependence in Turkish subjects with childhood ADHD starts early and is relatively resistant to treatment. Early diagnosis and treatment of ADHD might help prevent alcohol- and substance-related disorders.