INTRODUCTION: Many studies have been conducted in recent years to determine the safest and most effective methods for managing the common problems of mouth-breathing and respiratory disorders in children, and it is now accepted that CT is the examination of choice for the evaluation of the paranasal sinuses and adjacent structures, while functional endoscopic sinus surgery (FESS) represents the most advanced treatment of sinusitis. OBJECTIVE: To identify the key findings in preoperative CT scans of pediatric patients undergoing FESS. REPORT: A retrospective study was conducted on 50 patients between the ages of 2 and 15 years, treated for sinus disease at a clinic in the city of Blumenau. Computed tomography (CT) images were analyzed for changes in the paranasal (maxillary, ethmoid, sphenoid and frontal) sinuses, presence of abnormalities in the bony and cartilaginous parts of the nasal septum, presence of adenoid hypertrophy, anatomical characteristics of the inferior and middle turbinates, and others. History of prior otorhinolaryngologic surgery was obtained. The average age of patients was 10.5 years, and 24% of patients had had previous surgery. Among the CT findings, 88% of patients had hypertrophy of the inferior turbinate and 84% had a deviated nasal septum. The maxillary (74%) and the ethmoid (50%) were the commonest paranasal sinuses that had changes demonstrable on CT scanning. CONCLUSION: The maxillary and ethmoid sinuses were the most commonly affected paranasal sinuses. Inferior turbinate hypertrophy, septal deviation, and middle turbinate polyps were the most common CT findings.