Rehabilitation increasingly addresses the International Classification of Functioning, Disability and Health's (ICF) concepts of activity and participation, but little is known about associations between changes in body functions and structures, activity, and participation. We conducted a before-and-after study of 35 ambulatory children with spastic diplegia or hemiplegic cerebral palsy, mean age 5 years 6 months (SD 2 y 2 mo). Children were in Gross Motor Function Classification System (GMFCS) Levels I (n=11), II (n=12), or III (n=12). We assessed body functions and structures, activity, and participation at baseline and at 2 months and 6 months post-botulinum toxin type A (BoNT-A) injection. Repeated-measures analysis of variance evaluated change, and linear regression assessed relationships. Baseline score relationships were moderate to strong but, despite similar directions of change at 2 months, change score relationships between measures of body functions and structures (spasticity and timed walk), activity (Gross Motor Function Measure and Pediatric Evaluation of Disability Inventory), and participation (Pediatric Outcomes Data Collection Instrument) at 2 months and 6 months were poor to fair (r<0.40). Predictor combinations accounted for <69% of variation in activity and participation change scores. Predictors often pertained to baseline score, GMFCS level, or age. Relationships between changes at different ICF levels are complex, and activity and participation gains post-BoNT-A are likely to be influenced by the child and environment factors.