The aim of the study is to determine the distances from outer and inner of bone walls to the position 3 mm from the apices and the width of lower bone at this position of the first lower molars in Vietnamese on ConeBeam CT Methods: The study was conducted on 166 patients who had exposured using CBCT indicated by dentists in Nguyen Trai Dental CT Central, HoChiMinh City, from October 2015 to June 2016.