Aim: This study investigates the correlation between crown size and the presence of a second mesiobuccal (MB2) canal in the permanent maxillary first and second molars. Materials and Methods: The study was conducted at Taibah University Dental Hospital (Madinah, Saudi Arabia) using CBCT scans from 331 patients. Two general practitioners examined CBCT scans under the supervision of a radiologist and endodontist. CBCT scans were acquired using a Kodac 9000 machine and measured with Kodac Carestream software. mesiodistal distance and bucco-palatal distance were measured from CBCT scans. In addition, patients' age and gender were recorded. Data was analyzed with IBM SPSS software, and statistical tests were employed to evaluate the presence of MB2 based on gender, crown width, and length. Results: The overall prevalence of MB2 in the upper first molars was 46.6%, and in the upper second molar was 45.1%. There is a correlation between the prevalence of MB2 and the size of the crown, which is significantly higher when the mesiodistal or bucco-palatal length is longer than 10 mm. Conclusion: There is a positive correlation between the presence of MB2 and the size of the crown. Further investigation should be performed with a higher number of cases.