This study aims to evaluate the sensitivity and specicity of CT in diagnosis of sinonasal diseases along with the spectrum of Paranasal sinus diseases oncomputerized tomography (CT) and correlate their clinical and histopathological ndings. 40patients who have undergone endoscopic sinus surgery, their relevant histopathological and surgical reports are included in Radiodiagnosis department of Nil Ratan Sircar Medical College. Chronic sinusitis has 100% sensitivity,94% specicity, 96% positive predictive value (PPV) and 100% negative predictive value (NPV). For fungal sinusitis the sensitivity was 66%,specicity was 97.4%, PPV 66% and NPV 97.4%. Polyps have sensitivity of 90.9%, specicity of 94%, PPV 90% and NPV 100% Benign neoplasms have sensitivity of 100%, specicity of 100%, PPV 100% and NPV 100%. CT may be used as gold standardimaging modality for evaluating the PNS diseases.