Introduction: Chronic otitis media (COM) has been an important cause of middle ear disease since prehistoric times. Despite the valuable contribution of antibiotics, COM remains a common disease and its complications challenge both otologists and radiologists. Chronic otitis media is relatively common and potentially dangerous disease of the ear. It is defined as permanent abnormality of the pars tensa or flaccida, most likely a result of earlier acute otitis media, negative middle ear pressure or otitis media with effusion. Chronic Otitis Media is of two types : Mucosal and Squamosal. COM of all types is associated with erosion of the ossicular chain . The incidence and degree of ossicular destruction is much greater in cases of unsafe CSOM, due to the presence of cholesteatoma and/or granulations. Although bone erosion may occur in COM without cholesteatoma, it is more frequent when the keratinizing epithelium is present. Aims: To compare the preoperative HRCT findings with intra-operative findings in patients with Chronic Otitis Media and to resolve the doubts about the sensitivity and specificity of pre- operative CT scan findings in squamosal COM. Materials and Methods: This is a prospective study of 50 patients done principally at the Institute of Otorhinolaryngology And Head & Neck Surgery, IPGME&R & SSKM Hospital , Kolkata, India in which patients coming with inactive or active squamous Chronic Otitis Media with or without complications, who were planned for different types of mastoid surgeries were included in the study . Result: This study has shown that HRCT imaging of temporal bones for COM accurately depict presence of soft tissue mass in either the external auditory canal or the middle ear subsites, the integrity of the scutum, the integrity of the ossicular chain and erosion of the tegmen or the sigmoid plate. However, the role of HRCT could not be established in predicting the status of the tympanic membrane, the presence of lateral semicircular canal fistula, integrity of the incudostapedial joint. HRCT alone as a diagnostic modality could not predict the nature of soft tissue with statistical significance. Conclusion: Preoperative CT scan is helpful in relation to diagnosis and decision making for surgery in cases of cholesteatoma and ossicular erosion. It provides information on anatomical variations and complications. It serves as a road map to assist the surgeon during surgery.