Purpose : The purpose of this study was to determine the prevalence of sinus opacification among adult dental patients. Materials and Methods : Five hundred and sixty-four Cone Beam Computed Tomography (CBCT) scans of dental patients over the age of 18 were reviewed for sinus opacification. Opacification was graded as clear, mild, moderate or severe. Patients with any sinus-related signs or symptoms were excluded. Results : Sinus opacification in one or more sinuses was found in 59.2% of the patients. The sinus opacification was mild in 49.8%, moderate in 8.3%, and severe in 1.1%. The maxillary (37.7%) and ethmoid (37.4%) sinuses were most frequently affected. The prevalence was higher in the older age group and showed a male predomination (p<0.05). Conclusion : Sinus opacification in asymptomatic adults is very common and emphasizes the importance of clinical correlation before deciding on the final diagnosis and treatment.