Background: The present study was undertaken for assessing the role of diagnostic nasal endoscopy as a pre-operative evaluation tool in patients with sino-nasal diseases. Materials & methods: The study was conducted at Chirayu Medical College and Hospital Bhopal (M.P) during a period from January 2023 to March 2023. 30 patients who presented with persistent complaints related to the nose and paranasal sinuses were evaluated by both diagnostic nasal endoscopy and CT PNS. All the patients were evaluated by both office nasal endoscopy and CT scan PNS. The nasal cavities were packed with Nasal decongestants like xylometazoline and 4 % xylocaine for 5 min and then removed the pack. Examination of the nasal cavity in a systematic fashion was done in supine position. The CT scans were performed. Any Sino-nasal finding in CT was considered as a positive scan. The diagnostic value of the findings of nasal endoscopy and CT scan PNS for the evaluation of sino-nasal pathology was compared. Results: On Nasal endoscopy, Significant deviated nasal septum, chronic rhinosinusitis without polyposis, Ethmoidal polyposis, Antrochoanal polyp, CSF Rhinorrhea, Inverted papilloma were seen in 10Patients, 7 patients, 5 patients, 5 patient and 1 patients, 2 patients respectively. Sensitivity and specificity of diagnostic nasal endoscopy in detection of sino-nasal diseases was 96 percent and 100 percent respectively. Conclusion: Nasal endoscopy is a valid and objective diagnostic tool in the work up of patients with sino-nasal diseases.