BACKGROUND: A number of studies have shown that facial asymmetry improves in congenital muscular torticollis (CMT) patients after surgical release. This study confirmed the improvement in facial asymmetry, and analyzed factors that affect the change of facial asymmetry in CMT patients after surgical release by using objective and quantitative methods. METHODS: Facial asymmetry was analyzed in 60 CMT patients who underwent surgical release before 10 years of age. Horizontal and lower facial asymmetry angles (HFAA and LFAA) in the clinical photograph were used to measure facial asymmetry. Postoperative improvements in HFAA and LFAA were evaluated in each age group, after grouping the patients by age. Patients were divided into 2 groups according to the postoperative head tilt and functional deficit. Postoperative improvements in HFAA and LFAA were compared between 2 groups. The relationships between postoperative improvements in HFAA and LFAA and independent variables (age, follow-up period, preoperative HFAA or LFAA, postoperative head tilt, and postoperative functional deficit) were analyzed. RESULTS: Mean age at operation was 34.8 months (range, 6-120 mo). Horizontal facial asymmetry angle was improved significantly postoperatively in groups <5 years of age. Lower facial asymmetry angle was improved significantly postoperatively in all age groups. No significant difference was found in the postoperative improvements in HFAA and LFAA between 2 groups according to the postoperative head tilt and functional deficit. In the correlation analysis, postoperative improvements in HFAA and LFAA were proportional to the follow-up period (r = 0.256, P = 0.048) and preoperative HFAA or LFAA (r = 0.600, P < 0.001). CONCLUSIONS: Facial asymmetry in CMT patients can be improved in part if surgical release is performed before 10 years of age and the possibility of improvement may be different according to the area of the face. After surgical release, facial asymmetry will improve over a long period of time, and patients with more severe facial asymmetry have a better remodeling potential to achieve facial symmetry.