With a growing consensus of the importance of physical activity across a number of health outcomes, the current study investigated the impact of a cancer diagnosis on adolescent physical activity behavior. Participants (n=97) completed a mailed, self-administered questionnaire in which they recalled their physical activity behaviors across the cancer experience. Examination of the data revealed that adolescents treated for cancer experience significant declines in physical activity that are not recovered following treatment completion. It is not clear if the sustained reduction in posttreatment physical activity is attributable to the lingering effects of cancer treatment, but the long-term implications of a reduction in physical activity may be far-reaching.