Evaluation of the accuracy of objective diagnostic modalities for chronic rhinosinusitis and their comparison to each other to reach the correct diagnosis with minimum cost and highest accuracy. Prospective diagnostic cohort study. Academic medical center. Subjects more than 10 years of age presenting for evaluation of chronic rhinosinusitis, not responding to 12 weeks of medical treatment, suffering from at least 2 or more of the following symptoms- nasal obstruction, anterior and or posterior nasal discharge, headache or facial pains, and abnormalities of smell were prospectively studied. All selected patients were subjected to nasal endoscopy and CT paranasal sinuses. Endoscopic findings were scored according to Lund Kennedy scoring system. Sinus CT scans were scored with the Lund Mackay scoring system. The clinical diagnosis of CRS was determined on the basis of the published adult sinusitis guideline criteria and nasal endoscopic findings were compared with the diagnostic gold standard CT. A total of 100 patients were studied. Endoscopy was able to diagnose 87 % as CRS based on Lund-Kennedy score ≥2. 93 % patients could be labeled as CRS based on Lund-Mackey score ≥4. On correlating endoscopy and CT PNS it was found that sensitivity was 88.04 %, specificity was 28.57 %, PPV was 94.19 %, NPV was 15.38 %. Positive likelihood ratio of 1.23 and negative likelihood ratio of 0.42 was found p value was found to be 0.10565, thereby confirming that there is no significant difference in diagnosing CRS by either modality. The addition of nasal endoscopy helps reduce the use of CT, reducing costs and radiation exposure.