Purpose: The purpose of the study is to quantify anteroposterior and transverse facial soft tissue changes with respect to underlying skeletal movements after sagittal split osteotomy (BSSO) by using cone beam computed tomography. Materials and methods: The study was conducted on six patients who required bilateral sagittal split osteotomy for correction of mandibular retrognathism. The patients were scanned using cone-beam computed tomography 1 week before the surgery, and 6 months after the surgery. The difference between pre- and post-operative images were measured and the ratios of different hard to soft tissue movements were calculated. Results: There was a statistically significant difference in the mean measurements postoperatively. The ratio of the mean hard to soft tissue movement after mandibular advancement was 1:0.97 in the chin region and 1:0.80 in the lower lip area. The mean decrease in MLF depth was 1.4mm and the mean increase in the MLA was (27.7o). Conclusion: The soft-tissue changes related to mandibular advancement would appear to be fairly predictable and follow their underlying skeletal structures in 1:0.97 ratio in the chin area.