The objective of this study was to investigate the effect of timely peritoneal dialysis (PD) catheter in children with abdominal compartment syndrome (ACS) while supported on extracorporeal membrane oxygenation (ECMO). We present a case series of four patients who developed significant intraperitoneal fluid accumulation and ACS at the general pediatric and cardiac intensive care units in a tertiary children's hospital. The hospital's ECMO database was queried for patients supported on ECMO who required PD catheter placement. These patients were assessed for clinical characteristics and outcomes. Four patients were identified with capillary leak syndrome associated with a primary diagnosis: cardiac transplant rejection in one, septic shock and acute respiratory distress syndrome in two, and neonatal hydrops fetalis in one patient. In each of these patients, a PD catheter was placed for severe abdominal distension and proven/suspected ACS. There was dramatic improvement in venous return after drainage of peritoneal fluid. Two patients were subsequently able to be separated successfully from ECMO support. One patient died of acute neurologic complication and the other because of severe gastrointestinal bleeding. After ruling out common causes for decreased venous return, ACS should be suspected as one of the important causes, especially in patients with massive capillary leak and increasing abdominal distension, among patients supported on ECMO. Timely placement of a PD catheter in patients who develop abdominal distension and ACS can substantially improve venous return and thus help maintain adequate tissue perfusion by improving ECMO flows. Copyright © 2012 by the American Society for Artificial Internal Organs.