Hemispherectomy has been used successfully for patients with medically intractable epilepsy. However, it is difficult to predict postoperative motor function. The aim of the present study was to analyze whether the preoperative asymmetry of cerebral peduncles could be used to predict motor function restoration before hemispherectomy for young patients with medically intractable epilepsy. The clinical record and magnetic resonance imaging data of 53 patients were analyzed retrospectively. The correlation between preoperative cerebral peduncle asymmetry ratio (pCPAR) and pre- and postoperative changes in motor function was evaluated, as well as the influencing factors for pCPAR, such as duration and etiology factors. The restoration of motor function was defined as changes in pre- and postoperative hemiparesis. The pCPARs of patients with improved and unchanged hemiparesis were significantly greater than that of worsened patients. Patients with a pCPAR of more than 1.5 had an obvious restorative capacity of motor function of the intact hemisphere, and these patients had a lower risk of worsening hemiparesis. The duration in the improved/unchanged and worsened groups was 5.84 ± 3.85 years and 2.67 ± 2.03 years, respectively. Furthermore, there were more patients with no-progressive pathology in the group in whom pCPAR was more than 1.5. pCPAR is a useful and objective indicator for predicting the restoration of motor function in pediatric patients with medically intractable epilepsy before hemispherectomy. Most patients with nonprogressive pathology and a duration of more than 5 years presented with greater pCPARs, exhibited better restoration of motor function, and had less risk of worsening hemiparesis. Copyright © 2018 Elsevier Inc. All rights reserved.