To examine the clinical and genetic characteristics of Korean male alcoholics with and without attention deficit hyperactivity disorder (ADHD). The present study included 85 male alcoholics who were diagnosed as having DSM-IV alcohol dependence. A total of 28 (32.9%) alcoholics were diagnosed as having DSM-IV ADHD with ongoing symptoms in adulthood. For the evaluation of their psychiatric conditions, the alcohol dependence scale (ADS), Beck depression inventory (BDI), Beck anxiety inventory (BAI), Barratt impulsiveness scale (BIS), brief anger-aggression questionnaire (BAQ), overt aggression scale (OAS), codependence test, and obsessive compulsive drinking scale (OCDS) were administered. The genotype frequencies of the dopamine type 2 receptor gene (DRD2), aldehyde dehydrogenase type 2 gene (ALDH2), functional polymorphism in the regulatory region of the serotonin transporter gene (5-HTTLPR), and catechol-O-methyltransferase gene (COMT) polymorphisms were examined. Compared with alcoholics without ADHD, the mean ages for the onset of pathological drinking and alcohol withdrawal hallucinations were significantly earlier in alcoholics with ADHD. There was also a significant difference in the history of antisocial behaviour between the two groups. Compared with alcoholics without ADHD, the mean scores of the ADS, BDI, BAI, OAS, and OCDS were significantly higher in alcoholics with ADHD. With regard to the codependence test results, the mean scores of the interpersonal problem, low self-esteem and anxiety/fear subscales, and the mean total score of the codependence test were significantly higher in alcoholics with ADHD when compared with those without ADHD. There were no significant differences in the genotype frequencies of the DRD2, ALDH2, 5-HTTLPR, and COMT polymorphisms between alcoholics with and without ADHD. The results of this study suggest that the comorbidity of alcohol dependence and ADHD in this Korean sample forms a distinct clinical phenotype that shows an increased severity of alcohol-related symptoms and behavioural/emotional problems and that ADHD is associated with an increased risk for the early onset of alcohol dependence in Korean male alcoholics.