We analyzed pre and post enhanced CT scans of eighty two pathologically proven patients among which forty none cases were pulmonary tuberculosis and thirty three patients primary lung cancer who had mediastinal lymphadenopathy with special attensions. to nodal architectures numbers and locations. The results were as follows: 1. Lymph nodes abnormality was found in its average number of 1.2 nodes in tuberculosis and 2.8 nodes in primary lung cancer. 2. The locations of abnormality lymph nodes were 4R(17.5%) 10R(17.5%) and 5(14,0%) in order of frequency in tuberculosis and 4R(17.6%) 10R(14.3%) and 7(14.3%) in order of fre-quency in primary lung cancer. 3. In the feature of post enhanced lymph nodes the central low density type was the most frequent in tuberculosis (61.4%) The most frequent in tuberculosis(61.4%) The most frequent type in primary lung cancer was the homogenous type (79.1%) 4, The incidence of lymph node calcification were as twice in tuberculosis (67.3%) than in primary lung cancer(39.4%) 5. In other findings parenchymal mass density(78.8% in Ca/12.2% in Tb) and pleural effusion (27.3% in Ca/10.2% in Tb) were more frequent in primary lung cancer but parenchymal calcification (17.3% in Ca/10.2% in Tb) were more frequent in primary lung cancer. but parenchymal calcification (27.3% in Ca/49.0% in Tb) was more frequent in tuberculosis The cavity formation of primary lung cancer(27.3%) was found to be as the same frequency as in tuberculosis(20.4%)