Objective — to assess the results of using balloon tracheal occlusion in fetuses as a method of in utero surgery for secondary pulmonary hypoplasia in the presence of congenital diaphragmatic hernia. Subject and methods. During 2014—2016, the Ural Research Institute of Maternal and Infant Care, Ministry of Health of Russia, analyzed the features of the course of pregnancy and labor in 19 women and those of the course of the neonatal period, the immediate results of postnatal surgical correction, postnatal outcomes, and the results of postmortem examinations in their neonates with secondary pulmonary hypoplasia associated with congenital diaphragmatic hernia. Five fetuses with lethal pulmonary hypoplasia in the presence of left-sided false congenital diaphragmatic hernia (a study group) at 26—27 weeks’ gestation underwent surgery for this condition through in utero balloon tracheal occlusion. A comparison group consisted of 14 women and their 14 newborns with left-sided congenital diaphragmatic hernia, who had not undergone in utero surgery for this condition. The comparison was divided into 2 subgroups according to the presence of lethal congenital pulmonary hypoplasia: 1) 7 women and their newborn infants without lethal pulmonary hypoplasia and 2) 7 women and their neonates with lethal pulmonary hypoplasia in the presence of left-sided congenital diaphragmatic hernia. Results. In the study group, the gestational age of the newborn infants followed up was significantly lower than that in the comparison group (34.2±0.6 and 37.7±1.7 weeks, respectively; p=0.006). However, the babies who had undergone in utero surgery for lethal pulmonary hypoplasia in the presence of left-sided congenital diaphragmatic hernia tended to have higher one-minute and five-minute Apgar scores than those who had not used intrauterine balloon tracheal occlusion. The course of an adaptation period was identical in premature newborns with lethal pulmonary hypoplasia, who had undergone in utero correction via balloon tracheal occlusion (the study group) and full-term newborns (Subgroup 1 of the comparison group) without lethal pulmonary hypoplasia, which confirm the period of general condition stabilization and that of surgical treatment for congenital diaphragmatic hernia in the neonatal period. All the infants with lethal pulmonary hypoplasia without in utero balloon tracheal occlusion surgery (Subgroup 2 of the comparison group) were born with a severe and extremely severe condition, did not receive postnatal surfactant therapy; the severe and instable status was a contraindication to postnatal surgery for congenital diaphragmatic hernia. In the study group, fatal outcomes were observed in 2 out of the 5 babies; in Subgroup 2 of the comparison group, all 7 newborns died from lethal pulmonary hypoplasia that had developed in the presence of congenital diaphragmatic hernia, who had not undergone in utero balloon tracheal occlusion. Conclusion. Congenital diaphragmatic hernia is now a severe and difficult-to-treat condition that has a high percentage of perinatal losses. The present investigation has shown that in utero balloon tracheal occlusion with prolonged secondary fetal pulmonary hypoplasia associated with congenital diaphragmatic hernia is the surgical method of choice and a reserve for lowering neonatal mortality rates.