Objective: Detecting solitary or multiple pulmonary cavitary lesions on multi detector CT scan of the chest and assessing the role and value of multi detector CT in diagnosing the nature and causes of pulmonary cavitary lesions. Materials and Methods: The study was conducted on a 16 slice multi detector CT scanner (GE BRIGHT SPEED ELITE 16 SLICE). Characterizing number, location, size, shape , margin, nodularity, internal characteristics of nodule as calcification , wall thickness , wall contour, satellite nodule and feeding vessel with associated changes of lymphadenopathy, consolidation and pleural effusion were investigated. Results: Out of 30 pulmonary cavitary lesion cases 21 (70%) were non-malignant and 9 (30%) were malignant cavities. Thick wall (>15mm) was seen in 83% of malignant cases. Central location, nodularity, spiculation, and lymphadenopathy were seen in 44%, 55%, 33%, and 55% malignant cases respectively. Thin walled cavities (<7mm) was seen in 93% of benign cases and most of them were due to tuberculosis. Conclusion: Thick walled solitary cavities with nodularity, spiculation, irregular margins, central location and marked lymphadenopathy were more frequently in malignant cases whereas multiple thin , smooth walled cavities with centrilobular nodules, associated consolidative areas and peripheral and upper lobe location were seen in benign cases.