This study investigated the diagnostic accuracy of CBCT for detection of accessory mental foramina (AMFs) in dry mandibles using two different devices and three different CBCT imaging modalities. A total of 40 dry mandibles (20 per group) were selected to generate corresponding CBCT images, each with three different CBCT imaging modalities (high, standard, and low doses), using ProMax 3D Mid (Planmeca) and Veraview X800 (J. Morita). The presence, count (n), location, and diameter of the AMFs were measured on both dry mandibles and CBCT scans. The Veraview X800 with different imaging modalities showed the highest accuracy (97.5%), while the ProMax 3D Mid in low-dose imaging modality exhibited the lowest accuracy (93.8%). The most common AMF sites on dry mandibles were anterior-cranial and posterior-cranial, while anterior-cranial was the most frequent on CBCT scans. As for AMF diameter, the mean mesiodistal and vertical diameters on dry mandibles were 1.89 mm and 1.47 mm, respectively, which were greater or equal to the values obtained from CBCT scans. The overall diagnostic accuracy for assessing AMFs exhibited good results, but some caution is warranted when using a low-dose imaging modality with a large voxel size (400 μm).