Objectives: To examine physical activity (PA), body composition, balance, and strength in youth (ages 10-18) with cerebral palsy (CP), compared to age- and sex-matched typically developing (TD) peers. Methods: Thirty youth with CP [gross motor function classification system (GMFCS) levels I-III; 20 males], were matched to TD youth. PA (minutes in sedentary, light, and moderate-vigorous) was measured using ActiGraph accelerometers. Body composition (fat and lean mass indices) was assessed by dual-energy x-ray absorptiometry. Center of pressure (total path length and 95% ellipse area) on two force plates represented balance. Lower-extremity strength was measured using hand-held dynamometry. Results: Youth with CP, GMFCS levels II or III, achieved less moderate-vigorous PA, were more sedentary, weaker with all lower-extremity muscle groups, had lower lean mass indices, and had larger 95% ellipse areas than TD youth. Conclusions: GMFCS level appeared to impact the severity of activity limitations and of body structure and functional impairments.