 A three-arm, randomized, double-blind, placebo-controlled, Phase 4, multicenter study to compare the efficacy and safety of atomoxetine versus placebo in children and adolescents aged 6 through 17 years with attention-deficithyperactivity disorder ADHD and comorbid oppositional defiant disorder ODD who are treated as outpatients in Germany. After an initial 3- to 28-day screening and washout phase, participants will be assigned to double-blind treatment with atomoxetine or placebo. A 2 week up-titration period will be succeeded by a 7 week treatment period at the target dose. The primary efficacy measure will be the Swanson, Nolan and Pelham Rating Scale Revised SNAP-IV ODD subscale score. 