Hydatid disease is a parasitic infestation caused by the larval stage of the tapeworm genus Echinococcus. In man the two main forms are due to E. granulosus and less frequently E. multilocularis. Man becomeds in-fected by contact with a definite host or by consuming contaminated water or vegetable. Hydatid disease is prevalent throughout much of the world such as the middle east eastem Australia cen-tral europe south America Alaska but it is very in Korea. We experienced one case of pulmonary hydatid disease. Chest films revealed ovoid mass in the left lower lobe and seen as unilocular water-density cystic lesion on chest CT which was removed surgically and then the pathology confirmed the diagnosis.