While passive range of motion (PROM) is commonly used to inform decisions on therapeutic management, knowledge of PROM of children with spastic cerebral palsy (CP) is limited. A population-based sample of 178 children with spastic CP (110 male; unilateral, n = 94; bilateral, n = 84; age range 4-17 years) and 68 typically developing children (24 male; age range 4-17 years) were recruited to the study. All children were able to walk a minimum of 10 m over a straight flat course, with or without assistive devices. Gross Motor Function Classification System (GMFCS) levels of participants with CP were: Level I = 55, Level II = 88, Level III = 21, and Level IV = 14. Ankle dorsiflexion, knee extension, popliteal angle, hip abduction, hip internal rotation, and hip external rotation were measured using a goniometer. The results indicate that the children with CP had significantly reduced PROM compared to the children with typical development. Children with CP demonstrated reduced length in the hamstrings, hip adductor, iliopsoas and gastrocnemius-soleus musculature, and contracture at the knee joint. Among children with CP, there were significant reductions in range with increasing functional limitation (higher GMFCS level) and variations based on unilateral or bilateral involvement. This was particularly the case for the hamstrings and hip adductor musculature, where PROM varied considerably across GMFCS Levels I to IV.