This study was conducted to assess the coincidence of mucosal hyperplasia in the maxillary sinus and related clinical diagnoses of posterior maxillary teeth found in cone beam computed tomography (CBCT) scans. A total of 204 patients who underwent CBCT examinations between 2006 and 2008 were evaluated retrospectively. Clinical and CBCT findings were correlated using patient records. Absolute frequencies, odds ratios (OR), and 95% confidence intervals (95% CI) were calculated for statistical evaluations. There was a pronounced association between periodontitis and radiological signs of sinusitis. Basal mucosal wall thickening was more likely in patients with decayed and non-vital teeth compared to patients with sound teeth (OR = 5.2; 95% CI = 1.2-23.1). Basal mucosal wall thickening was also more likely than total mucosal thickening (OR = 10.4; 95% CI = 2.6-42.2). Patients with decayed and endodontically treated teeth were more likely to exhibit involvement of the basal wall (OR = 9.2; 95% CI = 3.3-25.2) than were patients with healthy teeth. CBCT examinations revealed a correlation between basal mucosal thickening in the maxillary sinus and decayed posterior maxillary teeth or periodontitis. Chronic symptoms involving the sinuses are one of the most common reasons for patients to consult physicians. One reason for chronic orofacial pain is the prevalence of undiagnosed sinus conditions.