The present study was intended to define the relationship of radiological findings and pathological types of primary lung cancer. The 85 cases were selected after confirmation of the cell types by bronchoscopic biopsy, cervical lymph node or thoracotomy biopsy and lung resection. Results of the study were presented below. 1. Primary lung cancer is frequently developed after 4th decade and males were affected more frequently than females with ratio of 2 to 1. 2. The frequencies of pathologic cell types of lung cancer were presented as follows. Squamous cell carcinoma 40% Adenocarcinoma 25% Undifferentiated cell carcinoma 30% Alveolar cell carcinoma 5% 3. The findings of plain chest radiograph were presented as follows. In squamous cell carcinoma, hilar enlargement or hilar mass is the most frequent finding (53%) with atelectasis (26%) or obstructive pneumonitis (26%). In adenocarcinoma, pleural effusion is accompanied about half of cases (53%). In undifferentiated cell carcinoma, hilar mass with mediastinal widening and pleural effusion is frequent finding.