Background: Cone beam CT (CBCT) is an advancement of conventional CT that uses a divergent pyramidal or conical X-ray beam for imaging the craniofacial complex. Studies on the maxillary sinus and its relationship with the roots present within its close proximity are mostly based on computed tomography imaging and rarely being based on cone-beam computed tomography (CBCT). This study aims to determine the relationship of maxillary sinus and the mesiobuccal root of maxillary first molar using cone beam computed tomography (CBCT). Methods: The study was conducted in Armed Forces Institute of Dentistry (AFID) from Sept, 2019 to Feb, 2020. 142 CBCTs were studied in the duration of six months. The distance between the maxillary mesiobuccal root and floor of maxillary sinus was measured using the built in software. The data collected was analyzed using SPSS 23. p-value of <0.005 was considered significant.  Results: The mean distance was -0.85 mm ± 2.56 on left side and -0.74mm ± 2.40 on right side. There was no significant difference between left and right side. The correlation between age and left and right-side measurements was statistically significant, p-value 0.000. Conclusion: The relationship of maxillary sinus and the mesiobuccal root of maxillary first molar is significant. The study shows that in dentate healthy patients, the maxillary mesiobuccal molar root is nearly in contact with the sinus floor. These findings lead to the conclusion that performing surgical procedures in maxillary molar region may invariably lead to sinus perforation if one is not care full. Keywords:  Cone beam computerized tomography, Dental implant, Maxillary sinus, Molar