This fact sheet provides basic information on attention-deficit/hyperactivity disorder (ADHD) in children and describes an approach to getting services and supports, called “systems of care,” that helps children, youth, and families thrive at home, in school, in the community, and throughout life. In a classroom of 30 children or youth, it is likely that at least two students are affected by ADHD. This surprisingly common condition makes it hard for children and youth to control their behavior (sit still, think before speaking or acting, etc.) and/or to pay attention. If left untreated, it can lead to school or job difficulties, depression, relationship problems, and substance abuse.