Chest CT is the most useful modality in the diagnosis of primary lung cancer, particularly in patients with recurrent pneumonia which are resistant to antibiotic therapy and in high risk age groups for cancer. The purpose of this examination is to assess the usefulness of CT in pneumonic types of lung cancer. The authors retrospectively analyzed 15 histologically proven cases of pneumonic type lung cancer, which had no evidence of primary lung mass, mediastinal lymphadenopathy or other metastatic lesion on plain chest radiography. On CT scan, a primary lung mass was identified in 13 patients(87%), bronchial obstruction was identified in 12 patients(80%), and metastatic foci was found in the bone(one patient), liver(one patient), and spleen(one patient). In Conclusion, CT scan is a useful method to detect the mediastinal lymphadenopathy or pulmonary mass and also should be the initial radiolographic procedure for diagnosis of lung cancer in patients with recurrent pneumonia on imple chest radiography.