OBJECTIVES: To investigate whether the use of continuous renal replacement therapy is independently associated with increased in-hospital mortality in children on extracorporeal membrane oxygenation. DESIGN: Retrospective, 1:1 propensity-matched cohort study. SETTING: Tertiary PICU. PATIENTS: Eighty-six children on extracorporeal membrane oxygenation, 43 of whom also received hemofiltration. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Demographics, pre-extracorporeal membrane oxygenation hemodynamic data, fluid status, and biochemistry tests were collected, as well as duration of extracorporeal membrane oxygenation, blood product use, complications, and mortality. Forty-three children receiving extracorporeal membrane oxygenation and continuous renal replacement therapy were matched to a cohort of 43 children on extracorporeal membrane oxygenation not receiving continuous renal replacement therapy. The main indication for hemofiltration was fluid overload in 29 patients (67.4 ), renal failure in nine patients (20.9 ), and electrolyte abnormalities in five patients (11.6 ). The median duration of hemofiltration was 108 hours (47-209 hr). Patients receiving hemofiltration had a longer duration of extracorporeal membrane oxygenation (127 hr [94-302 hr] vs 121 hr [67-182 hr]; p = 0.05) and received more platelet transfusions (0.91 mL/kg/hr [0.43-1.58 mL/kg/hr] vs 0.63 mL/kg/hr [0.30-0.79 mL/kg/hr]; p = 0.01). There were otherwise no differences in mechanical or patient-related complications between both groups. There was no difference in the proportion of patients who were successfully decannulated (81.4 vs 74.4 ; p = 0.44), survived to ICU discharge (65.1 vs 55.8 ; p = 0.38), or survived to hospital discharge (62.8 vs 48.8 ; p = 0.19) in the controls versus the hemofiltration group. CONCLUSIONS: In-hospital mortality was similar between children on extracorporeal membrane oxygenation with and without hemofiltration although hemofiltration appeared to be associated with a slight increase in the duration of extracorporeal membrane oxygenation and more liberal platelet transfusions.