Objective: To determine the diagnostic accuracy of computed tomography (CT) of paranasal sinuses (PNS) in detecting fungal sinusitis keeping fungal culture as the gold standard. Study Design: Cross-sectional validation study. Place and Duration of Study: Department of Radiology, Combined Military Hospital, Rawalpindi Pakistan, from Jun 2018 to Jun 2019. Methodology: A total of 323 patients of either gender were included in the study (aged from 10-70 years). All the patients underwent plain CT scans of paranasal sinuses, and the CT scan findings were reported and recorded on pre-designed proforma. Results were then compared with the culture report of each patient respectively. Results: Among all the patients undergoing CT scans, paranasal sinuses 177 were True Positives, while 07 were False Positives. Out of a total of 139 CT scan-negative patients, 6 (False Negative) had fungal sinusitis on culture, whereas 133 (True Negative) had no fungal sinusitis on culture (p=0.001). Overall sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of CT scan Paranasal sinuses were 96.72%, 95.0%, 96.20%, 95.68% and 95.98%,respectively. Conclusion: CT scan of paranasal sinuses is a highly sensitive and accurate non-invasive investigation in detecting fungal sinusitis.