Attention deficit hyperactivity disorder (ADHD) is a common behavioral disorder found in children. Comorbid disorders, including oppositional/aggressive behaviors and emotional disorders, may be present in the majority of children diagnosed with ADHD thus complicating an optimal choice of pharmacotherapy. We evaluated the comorbid disorders in an out-patient sample of 76 children with ADHD (59 boys and 17 girls) aged 5-11 years using the Russian version of Kiddie-Shedule for Affective Disorders and Schizophrenia - Present and Lifetime Version. In all cases, a diagnosis met ICD-10 diagnostic criteria. Only 23 (30,3%) subjects had pure ADHD and 53 (69,7%) suffered from at least one comorbid disorder, i.e. oppositional defiant disorder (43,4%), anxiety disorder (39,5%), tics (9,2%), nocturnal enuresis (17,1%) and encopresis (5,3%). The recently published data of double-blind placebo controlled studies are reviewed indicating that in children and adolescents with ADHD and comorbid disorders atomoxetine is superior to placebo in treating ADHD and alleviating the symptoms of comorbid disorders.