Chronic otitis media may be due to chronic mucosal disease or cholesteatoma. Differentiating the two is usually achieved by clinical examination. The computed tomography (CT) scan is the standard imaging technique for the temporal bone, but its exact role in the preoperative assessment of patients with chronic otitis media is controversial. In this retrospective study we compared preoperative CT results with operative findings in 50 patients who had scan between January 2003 and December 2007. We analyzed the clinical presentation and checked if CT scan confirmed or excluded the presence of cholesteatoma and if this was affected by previous surgery. We concluded that CT scan could not be relied on to differentiate cholesteatoma from chronic mucosal disease. It should be used selectively in the preoperative preparation only if complications of the disease suspected.