Background: Computed tomography (CT) scan plays a vital role in the diagnosis of CRS and in detecting its complications. It has the ability to detect mucosal disease and anatomical variations, to demonstrate a primary obstructive pathology and to visualise posterior ethmoid, sphenoid sinuses and thus helps in the management of CRS. Nasal endoscopy plays a main role in recognizing anatomical structural variations and mucosal changes of middle meatus and osteomeatal complex producing drainage block leading to CRS both in patients with normal CT and in patients with abnormal scans. CT scan offers information on anatomical variations, sinus status, and complications. To perform a CT scan simply to confirm CRS poses the unacceptable risk of additional exposure to ionizing radiation, not to mention the additional cost of the procedure. Aim of the srudy to evaluate the accuracy of Nasal endoscopy as compared to CT in diagnosis CRS Material & Methods: This was a cross sectional study, conducted over a period of 13 months during SEP 2020 – Dec 2021, in the Department of Otorhinolaryngology, of Career Medical College in Lucknow. Results: The male: female ratio of the present study was 3:2. The common finding was congested nasal mucosa in 27 patient (54%) and mucopurulent nasal discharge in 32 patient (64%) Septal deviation was found in 45 cases (90%) among that left DNS was in 27 cases (54%) and DNS with spur in 18 cases (36%). Out of total 50 patients, 41 (82.0%) had abnormal endoscopic findings while 44 (88.0%) patients were showing positive CT scan. Out of 8 patients having normal endoscopy, 3 patients had abnormal CT. But one patient who was CT scan negative was found to be endoscopic positive for CRS. The sensitivity of endoscopy was 93.2% and the specificity was 83.3%. Positive predictive value was 97.6% and negative predictive value was 62.5%. Diagnostic accuracy in diagnosing CRS was 92%. Conclusion:It is mandatory to do both CT scan a DNE in patients with chronic sinusitis, those who are planned for functional endoscopic sinus surgery. Both CT scan and DNE are complimentary to each other in the diagnosis of CRS.