All children are oppositional from time to time, particularly when tired, hungry, stressed or upset. They may argue, talk back, disobey, and defy parents, teachers and other adults in authority. Openly uncooperative and angry/hostile behavior becomes a concern when it is so frequent and consistent that it stands out when compared to other children of the same age and developmental level and when it affects the child’s home, school, and social life. The child with disruptive behaviors may have ADHD or the “externalizing behaviors” (i.e., acting out behaviors) may be the symptoms of anxiety or depression. There is significant overlap between attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD), the two conditions are often co-morbid. Current evidence-based guidelines for treating ODD recommend treating the ADHD symptoms first as the best initial approach. This chapter discusses the assessment and management of disruptive behaviors.