The aim of the study is to determine classifications of root canals of mandibular first molars according to Vertucci 1984 in Vietnamese on ConeBeam CT Methods: The study was conducted on 332 mandibular first molars of 166 patients who had exposured using CBCT indicated by dentists in Nguyen Trai Dental CT Central, HoChiMinh City, from October 2015 to June 2016.