Physical activity is important for young people's health. The emphasis over the last 2 decades has been on moderate to vigorous exercise when designing activity and exercise programs for children and adolescents with cerebral palsy (CP). Emerging evidence suggests that sedentary behavior is distinctly different from a lack of moderate to vigorous physical activity and has independent and different physiological mechanisms. The concept of concurrently increasing moderate to vigorous physical activity and replacing sedentary behavior with light physical activity may be beneficial for children and adolescents with CP. This article is a summary of the evidence for what works and what does not work for improving the physical activity of children and adolescents with CP. It also discusses what is known about sedentary behavior of children and adolescents with CP and what research directions are needed to build foundational knowledge in this area with this population.