Relationship between Attention Deficit Hyperactivity Disorder (ADHD) and obesity in adults and children had previously been established in research studies. Brain imaging studies pointed out the important role of the prefrontal region in both ADHD and obesity. However, the underlying link between ADHD and obesity is not well understood. The hypothesis that impulsivity could play a role has been explored in clinical studies of ADHD and Binge Eating Disorders or Loss of Control Eating, with contradictory results. Our study aims to compare children with ADHD and obesity to children with ADHD and normal weight. We propose to compare these two populations with clinical, neuropsychological and brain spectroscopy investigation, focusing specifically on impulsivity items.