Chest X-ray of a 28-year-old woman revealed an abnormal shadow in the right lower lung field and dextrocardia, for which detailed investigation was performed. Since the CT number of the tumor shadow corresponded to that of the liver on chest CT, diaphragmatic hernia of the liver was suspected, and was confirmed by MRI and angiography of the abdomen. In addition, the pulmonary artery and vein were hypoplastic, and angiography of the pulmonary artery demonstrated pulmonary hypoplasia. This case was considered to have primary pulmonary hypoplasia, because the dextrocardia was considered to have occurred secondary to pulmonary hypoplasia and the diaphragmatic hernia of the liver was not sufficiently large to cause pulmonary hypoplasia. Pulmonary hypoplasia first diagnosed in adulthood is rare, with a clinical course and roentgenographic appearance differing from those of pulmonary hypoplasia in children.