Background: Cone-beam computed tomography (CBCT) was developed because of studies demonstrating its value in enhancing vision of the nasal cavity, lateral nasal wall, osteomeatal complex, and sinuses prior to functional endoscopic sinus surgery (FESS). Objective: The aim of the current work was to detect paranasal sinus diseases and anatomical variants in patients with chronic sinusitis identified prior to sinus surgery by CBCT and intraoperative during FESS. Patients and Methods: This study included a total of 30 patients with chronic sinusitis scheduled for FESS, attending at Department of Otolaryngology, Head and Neck Surgery, Zagazig University Hospitals. Results: The current research demonstrated consistent findings between CBCT and FESS in patients with chronic rhinosinusitis. Statistically significant (P<0.001) agreement was found between CBCT and FESS in the diagnosis of nasal deviation and concha bullosa. For nasal polyp and OMC blockage, the correlation between CBCT and FESS was statistically significant (P<0.001). The sensitivity and NPV of CBCT with respect to FSSS were both 100%, and the agreement between the two methods for detecting infundibulum thickening was statistically significant (P<0.001). Exceptions include nasal deviation and a thickened infundibulum, but otherwise, specificity is very good (67 percent and 70 percent respectively). Additionally, PPV was quite high except for nasal deviation, which was just 70%. Conclusion: It could be concluded that CBCT and FESS yield similar results when examining the paranasal sinuses. Diagnostic sinus endoscopy for the evaluation of chronic rhinosinusitis syndrome (CRS) is not always appropriate, but CBCT would be a suitable option due to its high accuracy, reduced costs, and lower radiation doses.