Purpose : The purpose of this study was to determine the prevalence of sinus opacification among dental paediatric patients. Materials and methods : Two hundred and eight Cone Beam Computed Tomography (CBCT) scans of dental patients under the age of 18 were reviewed for sinus opacification. Patients with any sinus-related signs or symptoms were excluded. Results : The overall prevalence of sinus opacification was 48.1 %. The ethmoid (28.4%) and maxillary (27.8%) sinuses were most frequently affected. There were no statistically significant differences for both age and gender. Conclusion : The high prevalence of sinus opacification in asymptomatic children emphasizes the necessity of clinical correlation. (Korean J Oral Maxillofac Radiol 2008; 38 : 219-23)