Background: There are considerable anatomical variations the nasal cavity that may interfere with normal nasal function and predispose to recurrent or chronic sinusitis. Functional endoscopic sinus surgery restores normalcy by working on the key regions rather than on the larger sinuses. The aim of the current study is to study the various anatomical variations which are present in patients undergoing endoscopic sinus surgery. Methods: A prospective study of sinus diseases using diagnostic endoscopy and computed tomography was conducted in the Department of ENT, Govt. ENT Hospital, Koti, Hyderabad. All the patients attending the ENT outpatient department, who had chronic sinusitis, not responding to the medical line of treatment and who were willing to undergo Functional Endoscopic Sinus Surgery. Sample Size: 50 Sampling: Prospective Study. Results: Keros Type I: 6 (10%), Keros Type II: 32 (68%), Keros Type III: 12 (22%). Septal deviations were seen in 29 (58%). Of these n=10 (34.03%), were to right and n=19 (65.5%), were to the left. Septal spurs were seen in n=18(36%) cases. Of these n=8(16%), were to right and n=10(20%) cases were to the left. Pneumatization of the septum was found in n=3(6%). Agger Nasi: Pneumatization of agger nasi was seen in n=29(58%) cases. Conclusion: Inferior turbinate enlargement in association with ipsilateral maxillary sinusitis was commonly noted. Most of the cases were Keros Type II category based on the Depth of Olfactory fossa. Therefore, through CT scan along with diagnostic nasal endoscopy must be done in whom anatomical variations are the cause of chronic sinus mucosal diseases.