To evaluate the prognostic significance of fetal lung mass diagnosed in utero. Prospective study of all cases with fetal lung mass referred to our center. Maternal fetal medicine specialists performed the prenatal ultrasound and postnatal follow-up was obtained in all cases. The cases were presented to the Prenatal Diagnosis Committee. Thirteen cases with fetal lung mass were examined. Expert ultrasound and fetal MRI identified: cystic adenomatoid malformation (CAM) (nine), lung sequestration (three), larynx atresia (one). Ultrasound was accurate in 12/13 cases. One fetus with lung sequestration had CAM type I also. Of the cases with CAM, 55% was type III, one of them had an extra—lung malformation. Polyhydramnios was present in three patients and one case had fetal hydrops. 44% of the CAM cases born at term and three of the all cases with CAM required surgical treatment. A wide range of lung malformations can be recognized in the fetus. Antenatal categorization of the abnormal findings is difficult and not always precise. The knowledge of the prognosis allows for parental counseling.