<AbstractText>Distraction osteogenesis can be used to treat hemifacial microsomia in patients of any age group. Application of three-dimensional (3D) technology in the surgical planning of distraction osteogenesis allows the placement of an intraoral distractor to define the cutting line and help predict the outcome of surgery.</AbstractText><AbstractText>This study compared the results of distraction osteogenesis performed, using computer-assisted surgery, on OMENS-plus-classified M2A, M2B, and M3 type patients. Comparisons were in terms of either accuracy or predictability.</AbstractText><AbstractText>40 patients were selected to participate in the 8-month study. Preoperative image data from 3D-CT scans of the 40 patients were translated into DICOM format 3D cephalometrics, run using the computer software MIMICS version 18, and based on eight reference anatomical landmark points, five lines of measurement, and the midline of the mandibular plane. The distraction vector for the affected side of mandible was selected and the elongation process simulated repeatedly until satisfactory results were obtained. The surgical guide was created using CAD/CAM-RP technology. The distraction osteogenesis procedure was then performed using the surgical guides. Follow-up for all patients continued until 8 months postoperatively. Accuracy with and without computer-assisted surgery was assessed linearly and volumetrically. Simple mean comparisons and paired t-tests were conducted using IBM SPSS V21.</AbstractText><AbstractText>In those patients who received computer-assisted surgery, distraction in the M2A type mandible showed accuracy of around 97.77% ± 7.92% (p > 0.05) for height and 97.91% ± 10.23% (p > 0.05) for length of the mandible. Meanwhile, the M2B type mandible presented accuracy of around 93.85% ± 8.07% (p > 0.05) for height and 95.85% ± 10.16% (p > 0.05) for length. For the M3 type mandible accuracy was around 98.42% ± 6.58% (p > 0.05) for height and 97.14% ± 11.45% (p > 0.05) for length. These measurements showed no significant differences between preoperative design and real outcome.</AbstractText><AbstractText>Individualized guides improve the accuracy of distraction osteogenesis. They help the surgeon to identify the mandibular defect and ensure the desired outcome after the operation.</AbstractText>