We reviewed our experience with fetal therapy for congenital cystic adenomatoid malformation of the lung (CCAM) at the University of California, San Francisco Fetal Treatment Center. Fetuses with life-threatening CCAM were selected for prenatal treatment according to predetermined guidelines, including the gestational age of the fetus, the size of the intrathoracic lesion, maternal health, and the development of fetal hydrops. The knowledge that fetuses with hydrops are at high risk for fetal or neonatal death led to fetal surgical resection of the massively enlarged pulmonary lobe (fetal lobectomy) in six cases. In the first case, resection was too late, since preoperative labor and maternal preeclampsia could not be reversed, leading to premature delivery of a nonviable infant. In the next four cases, CCAM resection led to resolution of the hydrops, impressive in utero lung growth, and neonatal survival. Right middle and lower lobe resection in the sixth fetus at 21 weeks was successful, but subsequent inexplicable fetal death highlights the need for better postoperative fetal monitoring and treatment. Three other fetuses with a single predominant cyst underwent thoracoamniotic shunt placement alone; two survived after delivery and prompt neonatal surgery with the assistance of high-frequency ventilation or extracorporeal membrane oxygenation. Fetal therapy can now be considered for otherwise fatal space-occupying intrathoracic lesions in the fetus.