The purpose of the study is to compare atomoxetine hydrochloride and methylphenidate hydrochloride in pediatric patients with ADHD.

Inclusion Criteria:

• Be at least 6 years of age and not more than 16 years of age at Visit 1
• Must meet DSM-IV criteria for ADHD
• Must be of normal intelligence (that is, without a general impairment of intelligence and likely, in the investigator's judgement, to achieve a score of greater than or equal to 70 on an IQ test)
• Must be able to swallow capsules
• Must have laboratory results that show no significant abnormalities (significant would include laboratory deviations requiring acute medical intervention or further medical evaluation)

Exclusion Criteria:

• Weigh less than 20 kg or more than 60 kg at study entry
• Have a history of Bipolar I or II disorder, psychosis, or pervasive developmental disorder
• Meet DSM-IV criteria for an anxiety disorder
• Have a history of any seizure disorder (other than febrile seizures)or prior ECG abnormalities related to epilepsy, or subjects who have taken or are currently taking anti-convulsants for seizure control
• Have a history of severe allergies to more than 1 class of medications or multiple adverse drug reactions,including a hypersensitivity to methylphenidate