The Aim of the Study: Was to identify the features of the anatomical structure of the root canals of teeth according to CBCT data in patients in different age groups., Material and Methods: Patients of europeoid race, both sexes, who have indications for endodontic treatment (60 people), were divided into three groups: group 1 (young) 20 people aged 18 to 44 years, group 2 (middle age) 20 people - from 45 to 60 years, group 3 (elderly) 20 people - from 61 to 75 years old. To assess the root canal anatomy, all patients underwent x-ray examination (CT) on a Vatech computed tomography and analyzed with the Ez3D plus program before beginning endodontic treatment. The object of study was the first molars of the lower jaw (distal root canal)., Results: The analysis of axial, sagittal, coronal sections of the first molar of the lower jaw revealed that patients belonging to the 1 st group, the distal root canal often had an oval shape all over (95%) and over a wide apical opening, in only one case out of 20 (5%) were identified at slit-like form of the distal root canal, probably due to malocclusion or as a consequence of increased abrasion of teeth. In group 2, two independent root canals were identified in the distal root of the first lower molar (in 65%), extending from the tooth cavity to the apex.in 35% of cases, the distal root canal began with a single entrance in the oral part and bifurcated into two separate channels at about the level of 2 /3 canals, then re - joined into a single apical opening, in group 3, in 75% of cases, a slit-like form of the distal root canal was observed. The obtained CLCT data (taking into account the image error) were confirmed in the clinic at the stage of endodontic treatment using optical magnification (microscope)., Conclusion: CBCT and operation microscopy with x40 magnification data showed clear age-dependent variations of first lower molar distal root canal anatomy.