One condition that requires special attention in the management of fetal cystadenoma of the lung is a type of emphysema that is even less common than cystadenoma. Among the cases judged as pulmonary cystadenoma type III by fetal ultrasound, one may be emphysema rather than cystadenoma, but currently it cannot be identified by prenatal ultrasound and requires additional MR examination, but the positive rate is not high, with the following characteristics: 1. In terms of incidence, cystadenoma is much higher than emphysema; 2. 3. symptoms appear early after birth, including dyspnea and hypoxia; 4. postnatal CT enhancement can clearly diagnose and distinguish; 5. lesions are more frequent in the upper lobes of both lungs, and if one lobe of the lung is involved, early symptoms of pulmonary dysplasia appear; 6. deformation of the thorax can appear; 7. mortality rate is higher than that of cystadenoma; 8. early surgery after birth is the best treatment. We have encountered 6 cases so far, and except for one case that gave up treatment and died, all 5 cases were cured by surgery in the neonatal and infant period, but the treatment period was significantly higher than that of cystic adenoma. And one case presented with severe thoracic deformity. It requires special attention in the diagnosis of fetal pulmonary cystadenoma, and it is unclear whether it is related to the poor prognosis of type III.