<p class="abstract"><strong>Background:</strong> The anatomy of paranasal sinuses is very complicated. Evaluation of the location, extent of sino nasal diseases and anatomical variations by preoperative radiologic evaluation of the paranasal sinuses is essential in planning surgical intervention. Meticulous radiographic delineation of the small structures in this region, coupled with endoscopic evaluation, provides detailed preoperative information regarding morphology and pathology.</p><p class="abstract"><strong>Methods:</strong> Patients with sinonasal symptoms indicating requirement of CT scan evaluation and aged more than 10 years were included in the study. Each CT scan was interpreted by an otolaryngologist and a radiologist and interpretation was by consensus. The data collected was evaluated and results are reported as rates and proportions. </p><p class="abstract"><strong>Results:</strong> Sinusitis (single or multiple sinus involvement), nasal polyposis, frontal mucocele and ethmoidal carcinoma with destruction of medial wall of maxilla were the pathologies observed in these CT scans with sinusitis [22 (43.1%)] being the most common pathology observed. Deviated nasal septum [21 (41.2%)] was the most common anatomical variation observed. All patients who had concha bullosa [5 (9.8%)] were observed to have sinusitis involving multiple bilateral PNS. Based on Keros’ classification, olfactory fossa depth type I was most commonly observed followed by type II and type III.</p><p><strong>Conclusions:</strong> CT scan is important in patients undergoing endoscopic sinus surgery for sinonasal diseases where it acts as a road map in identifying the presence, extent of disease and any anatomical variations. This pre-operative CT scan evaluation improves planning and helps in significantly reducing morbidity and possible complications during surgery. </p>