【Abstract】 Objective To evaluate the effect of continuous veno-venous hemodiafiltration (CVVHDF) on acute renal failure (ARF) following cardiac surgery in children. Methods CVVHDF therapy was applied to 11 ARF children following cardiac operation from July 2004 to July 2008. Results Of the 11 treated children, the mean age at the onset of CVVHDF was 30.6 months (6 months～12.4 years), and the mean body weight was 15 kg (9.4～30.8kg). The mean duration of renal replacement therapy was 62 hours (10~212 hours). Eight patients (72.7%) died in postoperative period, of whom 4 patients died of multiple organ dysfunction syndrome during CVVHDF without recovery of renal function, 2 died of cardiac failure, one died of respiratory failure, and one died of subarachnoid hemorrhage. In survival patients, BUN and Scr decreased after CVVHDF for 24-hour (P＜0.05). Recovery of renal function was found in 7 patients (63.6%). After CVVHDF for 48-hour, mean artery pressure (MAP) increased significantly (P＜0.05), and heart rate (P＜0.05) and central venous pressure (P＜0.05) decreased. Conclusions CVVHDF may be an effective measure for children with renal failure after cardiac surgery. CVVHDF improves renal function and stabilizes hemodynamics. However, the prognosis is predominantly determined by the primary diseases and the degree of postoperative heart failure.