Purpose: This study was performed to analyze and compare the location of the mandibular lingula, the anatomical position of the mandibular canal, and the thickness of the buccal cortical bone in normal occlusion and skeletal Class III malocclusion patients. Materials and Methods: Sixty patients who visited Seoul National University Dental Hospital and took Computed Tomography (CT) image from March, 2008 to September, 2011, were selected and divided into Angle classification I and III. Using the three dimensional imaging software(SimplantⓇ version 14.0, Materialise, Leuven, Belgium), the location of the mandibular lingula, the anatomical position of the mandibular canal, and the buccal cortical bone thickness were analysed. Measurements were statistically analyzed by Independent samples T-test. Results: In the comparison between two group, there were statistically significant differences in the height of the mandibular lingula from the occlusal plane (7.80±2.49 mm in Class I patient group and 10.03±3.31 mm in Class III patients group), and the ratio of the antero-posterior length of ramus of mandible to the length between the mandibular canal and the anterior point of the plane that was paralleled with the occlusal plane and contained the #46 CEJ in the ramus of mandible between Class I and Class III patient group. Other values in the rest of the measuring points did not show statistically significant difference. Conclusions: In our study, Classs III patients had higher mandibular lingula than Class I patients. Therefore, incision and osteotomy lines have to be considered under theses anatomical findings during mandibular surgery. (JOURNAL OF DENTAL IMPLANT RESEARCH 2013;32(2):25-32)