Injury to the contents of the mental foramen (MF) can be minimized by using cone beam computed tomography (CBCT) to determine the exact location of the MF prior to surgical procedures. In this retrospective study, variations in the vertical position of the MF between adult men and women older than 18 years were investigated using CBCT. The distance between the superior border of the MF and the most apical aspect of the cementoenamel junction (CEJ) of the mandibular second premolar was measured. Among the randomly accessed CBCT records of 200 patients, 176 MF-CEJ measurements met the inclusion criteria. There was a statistically significant difference (P < 0.001) between the sexes in the location of the MF. The distance in women was shorter by an average of 2.00 mm, irrespective of the side of the mandible. Additionally, a within-sex asymmetry between right and left sides was observed; the asymmetry was significantly greater in men than in women (P < 0.05). Clinicians should be cognizant of the influence of the patient's sex on the vertical position of the MF and the presence of asymmetry in the position of the MF between the right and left sides of the mandible within the sex groups.