Background: The success of endodontic treatment depends on the knowledge of root canal system. The root canals have complex morphology and wide individual variations. The aim of this study was to evaluate the root canal morphology of the maxillary first molars among residents of the Moscow region using cone-beam computed tomography (CBCT) scanning. Materials and Methods: Three hundred CBCT images of patients aged 20-70 years old were analyzed to study the root canal system (the number of canals and the configuration according to Vertucci's classification) of the maxillary first molars. The prevalence of a second mesiobuccal (MB2) in the mesiobuccal root (MB) was recorded in each age group. Results: three separated roots of the maxillary first molar were observed in 100% of cases. MB2 canals were found in 59.8% of cases. A second distobuccal canal was observed in 0.5% of cases. The canal morphology in the MB root was 40.2% in Type I, 22.4% in Type II, and 37.3% in Type IV. Conclusion: The prevalence of MB2 canals was 59.8%, and the most common canal morphology was Vertucci's Type I. Using CBCT scanning is a useful technique to evaluate and analyze the root canal system. © 2018 Contemporary Clinical Dentistry | Published by Wolters Kluwer - Medknow.