The purpose of this study was to evaluate the effectiveness of calcaneal lengthening in the treatment of planovalgus foot deformity of children with spastic cerebral palsy. Sixteen children (27 feet) with spastic cerebral palsy underwent calcaneal lengthening along with peroneal tendons. The results were assessed clinically and radiographically. Over an average of 3.2 years of follow-up (2.0-5.0), 20 (74.1%) feet showed a satisfactory clinical result, and 21 (77.8%) feet showed a satisfactory radiographic result, according to the modified Mosca's criteria. Dependent ambulators with severe pes planovalgus showed unsatisfactory results compared with independent ambulators with mild to moderate pes planovalgus. These findings suggest that for severe pes planovalgus of children with cerebral palsy, it may be difficult to correct the foot deformity by calcaneal lengthening with peroneal tendons.