Knowledge of the craniofacial anatomic structures is fundamental for successful autogenous bone grafting surgeries in implant dentistry. In view of the limitations of panoramic radiography, as a bidimensional image, Cone Beam Computerized Tomography (CBCT) has become necessary, as it makes possible to observe potential segments of autogenous bone grafting for implant placement in edentulous regions. The aim of this paper was quantify the bone thickness using CBCT to measure the thickness of the vestibular cortical-medullary bone in the mandibular retromolar and molar regions, as donor segments for the patients. The scans were obtained from a Newtom QVT 9000 3G Aperio ® Tomograph. They were taken from mandibles of 50 patients. We obtained statistically significant differences between measurements of molar areas of men and retromolar area of women (p<0.05). The results of this research broaden the dentist’s knowledge about evaluating potential donor areas in the posterior region of the mandible, as regards the requirement of predictability. In conclusion, greater thickness of donor area was observed in both the male and female gender bilaterally, in the mandibular retromolar and third molar regions. Furthermore, upper segment region presented greater cortical thickness in all the studied regions.