Safety and Tolerability Study of ABT-089 in Children With Attention-Deficit/Hyperactivity Disorder (ADHD)

* Have voluntarily signed an informed consent form. * Meet diagnostic criteria for attention-deficit/hyperactivity disorder (ADHD) based on detailed evaluation and interview with parent(s). * Subject is generally in good health based on medical history, physical examination, clinical lab tests and ECG. * Subject weights at least 37 pounds (17 kg) * Female subjects of child-bearing potential must have a negative urine pregnancy test at screening and baseline and agree to comply with applicable contraceptive requirements. * Subject can swallow pills and subjects and parents are able to keep required appointments for clinic visits and all tests, including blood draws and examinations.

* Subject has a current or past diagnosis of bipolar disorder, psychosis, autism, Asperger syndrome, pervasive developmental disorder, tics, Tourette syndrome, mental retardation, seizure disorder or traumatic brain injury. * Current diagnosis of obsessive-compulsive disorder, eating disorder, anxiety disorder or depressive disorder requiring treatment of any kind. * Subject has a history of, or ongoing, serious medical problem. * Subject has a history of significant allergic reaction to any drug. * Subject is planning to begin any type of behavioral or psychotherapy for treatment of ADHD. * Subject requires ongoing treatment with any psychiatric medication.