Introduction: To assess the incidence and configuration of the second mesiobuccal (MB2) canal in maxillary first and second molars in an adult sub-population in London from cone beam computed tomography (CBCT) scans. Materials and methods: CBCT scans from the adult patient record database at a dental teaching hospital were selected and viewed using 3D viewing software. Each tooth was assessed, in 1 mm axial and 0.5 mm sagittal sections, to determine the presence of a MB2 canal and then categorised according to Weine's classification. Results: A total of 110 CBCT scans of 323 teeth (172 maxillary first molars and 151 maxillary second molars) from 57 male and 53 female patients were assessed. A MB2 canal was found in 60.5% of maxillary first molars but only 41.7% of maxillary second molars; when present, the most common configuration was two separate and distinct canals (Weine Type III) at 46.2% for maxillary first molars and 43.8% for maxillary second molars. Two separate canals merging to form one canal at the apex (Weine Type II) were found in 39.4% of maxillary first molars and 28.1% of maxillary second molars; whilst 14.4% of maxillary first molars and 26.6% of maxillary second molars had two or more canals at the apex (Weine Type IV). Conclusions: The high incidence of a MB2 canal in maxillary first and second molars was re-confirmed in this study and clinical strategies are needed to manage, especially, the most challenging Weine Type IV variety. CBCT has again proven to be an excellent imaging tool and useful for assessing complex root canal morphology. Keywords: cone beam computed tomography, maxillary first molar, maxillary second molar, root canal morphology, second mesiobuccal canal