The purpose of this trial is to test the effectiveness of atomoxetine in treating symptoms of ODD in children with ADHD and ODD.

Inclusion Criteria:

• Patients are male or female outpatients who are at least 6 years of age and not more than 12 years of age at study entry.
• Patients must meet DSM-IV diagnostic criteria for ADHD and ODD.
• If other comorbid conditions are present, either the ADHD or the ODD diagnosis must be the patient's primary diagnosis.
• Patients must have laboratory results, including serum chemistries, hematology, and urinalysis showing no significant abnormalities.
• Patients must have an ECG performed at study entry that is absent of any abnormality that, in the opinion of the physician, should exclude the patient.

Exclusion Criteria:

• Patients who weigh less than 20 kg or greater than 60 kg at study entry.
• Patients who have a history of Bipolar I or II disorder, psychosis, or pervasive developmental disorder.
• Patients who have a current diagnosis of Major Depressive Disorder ([MDD]; with or without psychotic features), PTSD, or CDRS-R total raw score >40 at study entry.
• Patients with a history of any seizure disorder.
• Patients determined by the investigator to be at serious suicidal risk.