Objectives: To investigate whether botulinum toxin type A (BTX-A) injection is more effective than radial extracorporeal shock wave therapy in reducing plantar flexor muscle spasticity in subjects with cerebral palsy. Methods: A total of 68 subjects with cerebral palsy were randomly allocated to BTX-A injection (Group 1) or radial extracorporeal shock wave therapy (Group 2) (first experiment; E1). Outcome was evaluated using the Tardieu V1 and V3 stretches, at 3 weeks, 2 months (M2) and M3 after baseline. At M6 subjects in Group 1 received radial extracorporeal shock wave therapy and subjects in Group 2 received BTX-A injection (second experiment; E2); outcome was evaluated as in E1. Treatment success was defined as improvement in foot dorsiflexion ≥10° when performing the V3 stretch at M2 in both experiments. Results: In both experiments mean V1 and V3 significantly improved over time. In E1 both treatments resulted in similar treatment success. In E2 fewer subjects treated with BTX-A injection reached the criteria of treatment success than did subjects treated with radial extracorporeal shock wave therapy, which was due to a carry-over effect from E1. No significant complications were observed. Conclusion: BTX-A injection is not superior to radial extracorporeal shock wave therapy in the treatment of plantar flexor muscle spasticity in subjects with cerebral palsy.