 Bipolar disorder BD is a chronic disorder that severely affects the normal development of children and adolescents. The disorder is associated with high rates of suicide tentative and high-risk behaviors like sexual promiscuity and drug abuse. Bipolar disorder in children is also associated with high rates of comorbidity, especially with Attention-Deficit Hyperactivity Disorder ADHD. There is a scarcity of clinical trials assessing the effects of medications in children with BD. Moreover, the frequent presence of comorbid ADHD might determine lower response to treatment. Aripiprazole is a novel anti-psychotic drug. Its mechanism of action seems to be related to a stabilization of dopaminergic transmission, acting as a partial agonist especially in dopaminergic D2 receptors. It also has effects in 5-HT1a serotonergic receptors. Thus, it might have a promising effect in children and adolescents with comorbid BD and ADHD. A retrospective chart review, recently published, suggests the efficacy of this drug in children with BD. This study aims to assess the efficacy of Aripiprazole a novel anti-psychotic drug for the treatment of 50 children and adolescents age range: 08 to 17 years-old with Bipolar Disorder comorbid with ADHD. The study design is an 6-week randomized, double blind, parallel group trial. Patients were randomized to either aripiprazole or placebo. The hypotheses are: 1 Aripiprazole will significantly reduce maniac scores compared to placebo; 2Aripiprazole will significantly reduce ADHD scores compared to placebo; 3 Aripiprazole will not be significantly associated to weight gain compared to placebo. 