Introduction: Chronic Otitis media is still a serious disease all around the world. The disturbance in the ventilation of the middle ear appears to play a major role in etiology of chronic otitis media especially in formation of cholesteatoma. The angle between the Reid’s plane and the eustachian tube (ET) decides the ventilating function of the eustachian tube. This study aimed to compare the mean of Eustachian tube- Reid’s plane angle in Chronic Suppurative Otitis Media (CSOM) patient with and without cholesteatoma. Objective: To compare the mean of Eustachian tube - Reid’s plane angle in Chronic Suppurative Otitis Media (CSOM) patients with and without cholesteatoma using high resolution computed tomography (HRCT) Temporal bone. Materials and Methods: This is a retrospective study of 2 patient groups. First group consisted of 50 patients with Chronic Otitis media with cholesteatoma and the second group consisted of 50 patients without cholesteatoma. The presence or absence of cholesteatoma was decided based on records of intra-operative findings and HRCT temporal bone reports. The Reid’s plane- ET angle was measured using High Resolution Computed Tomography (HRCT) of the temporal bones in both groups and compared. Results: The mean Reid’s plane-ET angle was 27.20 degrees in the first group with cholesteatoma with a standard deviation of +1.92. The mean Reid’s plane-ET angle was 31.69 degrees in the second group without cholesteatoma with a standard deviation of +2.25. Independent t test (student t test) used for analysis. t value was 10.709. p value was <0.0001. The findings were statistically significant. There was highly significant difference in mean Eustachian tube- Reid’s plane angle between group 2 and group 1 (it was higher among group 2 compared to group 1). Conclusion: The Reid’s plane-ET angle has a major role in assessing the eustachian tube dysfunction. A reduced Reid’s plane-ET angle noted in a pre-operative tomographic assessment gives clues about the possibility of cholesteatoma in chronic otitis media. This assessment will help the ear surgeon to plan surgery accordingly for better post-operative results.