BACKGROUND: Extrathoracic lung sequestration is a rare variant of a developmental malformation that can be diagnosed prenatally and should be included in the differential diagnosis of abdominal tumor-like formations. CASES REPORT: From 1996 to 2020, 70 children with confirmed lung sequestration were treated at the Children's City Hospital No. 1 in St. Petersburg. Of these, 29 had intralobar sequestration, and 41 had extralobar sequestration. Four of these patients were diagnosed with a rare extrathoracic (intraabdominal) form. All four were born full-term without clinical manifestations of the defect. Ultrasound examination of all children revealed a solid formation up to 3 cm in diameter, located in the upper left quadrant of the abdominal cavity or retroperitoneal space in the projection of the left adrenal gland. Due to the location of the formation and the inability to visualize the aberrant arterial vessel during ultrasound examination, the first two patients were differentially diagnosed with an adrenal tumor (neuroblastoma). The cancer markers were negative, and adrenal cortex hormones were normal. The children underwent multispiral computed tomography-angiography to clarify the diagnosis. In both cases, the diagnosis of intraabdominal extrapulmonary sequestration with a feeding arterial vessel extending from the thoracic aorta was confirmed. Two children, previously treated in the last two years, were diagnosed by the ultrasound examination results that enabled the visualization of an aberrant arterial vessel feeding the sequester. Indications for surgical treatment have been set. The parents of one child refused treatment. Three children underwent sequestration removal (two by laparoscopic access, one had a laparotomy). Histologically, extrathoracic sequestration in combination with cystoadenomatosis was confirmed. The postoperative period proceeded without complications. RESULTS: Long-term treatment results were observed in all operated patients for a period of four to 10 years. The assessment was performed based on complaints and ultrasound data. All patients matured and developed according to their ages. CONCLUSIONS: Extrathoracic lung sequestration is a rare type of defect that is subject to surgical treatment. This pathology should be included on the spectrum of differential diagnosis of tumorous formations of the abdominal cavity and retroperitoneal space in newborns. The main methods for postnatal diagnosis of the defect are ultrasound and multispiral computed tomography-angiography.