BACKGROUND Chronic Otitis Media (COM) is the bacterial infection of the mucoperiosteum of the middle ear cleft that has persisted for 12 weeks and above, characterised by persistant otorrhea, tympanic membrane perforation with varying degree of hearing impairment. In mucosal COM there is permanent perforation of pars tensa with or without inflammation of middle ear and mastoid. Pneumatization refers to both the process by which the epithelium expands into developing bone and the resulting interconnected air cells within the temporal bone. MATERIALS AND METHODS 25 patients attending ENT OPD, with profuse unilateral ear discharge lasting for more than 3 months were selected by purposive sampling method from April 2021 to March 2022 and was subjected to detailed history taking and clinical examination. All the active mucosal COM patients were treated with conservative medical management. The patients were subjected to HRCT temporal bone and results were analysed. RESULT The mastoid pneumatization patterns were found to be sclerotic in most cases followed by cellular then diploeic. The age group most commonly involved were 21-30 years. The sex most commonly involved were females. The ear most commonly infected was left ear. The mastoid pneumatization patterns in contralateral normal ear were found to be cellular in most cases followed by diploeic then sclerotic. CONCLUSION There is decreased pneumatization in diseased patients which is secondary to chronic inflammation and not congenital cause. Hypocellularity of mastoids is the effect of the disease not the cause for middle ear pathologies.