There have been various opinions in the classification and nomenclature of the lung cyst. but the recently approved by most of the clinicians and pathologists is as follows; Ⅰ. Congenital Pulmonary Cysts. A. Bronchogcnic cell type 1. Solitary 2. Multiple B. Alveolar cell type 1. Solitary(balloon cyst, pneumatocele) 2. Multiple C. Bronchogenic and alveolar types combinedⅡ. Acquired Pulmonary Cysts. A. Bullous emphysema B. Subpleural blebs.According to the statistical data by Weaver, etc, the incidence of the congenital lung cyst in young adults is 5 out of every 100,000. This writer has experienced 2 cases of congenital lung cyst, one without any clinical symptom and the other with the complaints of hemoptysis, which I am therefore reporting.