The aim of this study is to evaluate the anatomical characteristics of the posterior region of the mandible and their surgical relevance related to bone harvesting procedures. Fifty retromolar cone beam computed tomography scans were analyzed considering the donor site anatomies. For each site, linear measurements were taken of cross-sectional scans to record perpendicular distances between the mandibular canal (MC) and the vestibular and crestal bone walls. Data showed that the distance from the MC to the vestibular bone wall is lower in the ramus area than in the external oblique ridge area ( 2.00 mm in 26% of cases). However, the distance between the MC and the crestal bone wall is higher in the ramus area than in the external oblique ridge area. There is less bone thickness in the ramus area, and this could expose the inferior alveolar nerve to damage if osteotomies are performed with fewer depth limitations, as reported in the literature.