Background and objectives:Anatomy of the root canal system and determining the number and form of the canals are the most important steps for a successful root canal therapy without post-operative complications. The evidence supports the variability and complexity of maxillary molars. The aim of this study was to evaluate the prevalence of the additional mesiobuccal canals in the mesiobuccal roots, root canal configuration and root numbers of first and second permanent maxillary molars through the cone beam computed tomography (CBCT) technique. Methods:One hundred patients’ images taken of maxillary first and second molars bilaterally by cone beam computed tomography technique. Classification of first and second molar root canals was performed in accordance with Vertucci’s classifi- cation system. The patterns of anatomical variations in contralateral molars were classified according to the Zhang classification system. Results: The present study found that three roots were the most prevalent numbers of roots in the right and left, first and second molars, 96.0%, 75.0%, 97.0%, and 72.0%, respectively. In addition, the prevalence of additional mesiobuccal canals in both the right and left, first and second molars were 45.0%, 20.0%, 40.0%, and 27.0%, respectively. Conclusion: Tooth variant type I of Zheng et al classification and type I of Vertucci’s classification of the root canal system was the most prevalent type.