Background: Paranasal sinus diseases are commonly encountered in clinical practice. These include a wide spectrum of pathologies ranging from inflammatory to neoplastic. Clinical examination followed by imaging is the mainstay in making a correct diagnosis. Methods: 100 consecutive patients underwent CT scan in the department of Radiology using Siemens Somatom Definition Flash 128 slice MDCT scanner as per standard protocol. Images were acquired in the axial plane with reformation in coronal and sagittal planes. Results: Most of the patients were in the age group of 30-39 years. The most common pathology was found to be inflammatory sinonasal disease. The most common CT inflammatory pattern was the osteomeatal pattern. The most common benign tumour was found to be juvenile nasopharyngeal angiofibroma and the most common malignant tumour was squamous cell carcinoma of maxillary sinus. Conclusions: MDCT proved to be highly sensitive in classifying the lesions into clinically relevant categories, establishing the diagnosis, for delineating the extent and for prognostication. MDCT is the modality of choice for imaging because of its ease, availability, speed and ability to reveal anatomy of structures, commonly found variations, extent of disease process as well as subtle bone changes that are important in diagnosing lesions and most importantly guiding the surgeons to plan the operation.