The computed tomography of thorax has had considerablely less impact in patient management than that of head and abdomen, because the conventional chest radiolgraphy is a much more sensitive and accurate examination than the plain film studies of the head and abomen. It has progressively been identified that the computed tomography of chest is superior to the conventional radiolgrphy in detection of small pulmonary nodules including occult metastatic lesions. in evaluation of character of hilar enlargement, and in staging of known bronchogenic cancer. And especially in mediastinum, the computed tomography is superior to the any other conventional radiogrpahy in outlining lesions and determining character and extent of lesions. At the department of radiology, Kyung Hee University Hospital, 87 cases of computed tomography of chest were performed with EMI-CT 5005 whole-body scanner from October 1977 to August 1979. The results were as follows ; 1. The fifty eight cases of consid red to be pathologic findings were 23 pleural thickening and/or effusion, 14 bronchogenic carcinoma, 8 inflammatory lesions of lung parenchyme, 6 mediastinal lesions, 3 metastatic lesions, 3 COPD, 1 trauma, respectively. 2. no gravity-dependent change was noted in patients with chronic obstructive pulmonary disease (COPD) , which was frequently seen in normal subjects. Diminished numbers of pulmonary vessels was noted in COPD. 3. Small nodules in lung, retrosternal , posterior constophrenic and subpleurla regions, which were not found on conventional radiogrpahy, can be detected by chest CT. 4. Differentiation of dilated central pulmonary artery from pulmonary mass in enlarged hilum and determination of adjacent mediastinal invasion, manifested by obliterated fat plane, was possible. 5. The cases of mediastinal widening such as paraspinal lipomatosis, pericardial fat pad, teratoma, and bronchogenic cyst were sasily determined by means of measuring the attenuation coefficiencies. 6. Small amount of pleural and pericardial effusion was easily derected.