Objective: To examine the role of physical activity in determining the affect and executive functioning of children with symptoms of ADHD. Method: In Study 1, the association between physical activity and affect in the daily lives of children with varying degrees of hyperactivity was examined. In Study 2, children with ADHD were randomly assigned a physical activity or a sedentary task before working on a task requiring executive control. Results: Lack of physical activity was shown to relate to depressed affect, more strongly in participants with severe hyperactivity symptoms (Study 1). The physically active participants showed improved executive functioning after only 5 min of vigorous activity; the sedentary control participants showed no improvement (Study 2). Conclusion: These results indicate that interventions to increase the level of physical activity in children with and without ADHD might improve affect and executive functioning. (J. of Att. Dis. 2013, XX(X)1-XX)