OBJECTIVE Acute renal failure (ARF) is still a frequent complication following extensive cardiac surgery. Renal replacement therapy (RRT) modality preferences to treat critically ill children have shifted from peritoneal dialysis to continuous renal replacement therapy (CRRT), although the experience with the latter is still highly limited in the infants. METHODS We describe our results with continuous veno-venous hemodiafiltration (CVVHDF) in 25 children (15 males, 10 females) who underwent CRRT from 2001 to 2006 and were retrospectively reviewed. RESULTS We performed continuous veno-venous hemodiafiltration (CVHDF) using PRISMA (Hospal). The mean age at the onset of CRRT was 26 months (ranging from 7 days to 11.2 years) and the mean body weight was 14 kg. The mean duration of RRT was 67 h (8-243 h) with ultrafiltration rate 4.9 ml/(h kg); the mean filter "lifetime" was 31.5h. Anticoagulation was achieved with non-fractioned heparin infusion (21/25 cases) and enoxaparin (2/16). The mean creatinine concentrations at the beginning, 24, 48 and 72 h were as follows: 171, 100, 65 and 88 micromol/l. Of these 25 treated children, 19 died in the postoperative period (8 during CVVHDF). The mortality rate for the entire group was 76%. The main cause of death was cardiac failure and sepsis with multiorgan dysfunction (MODS). The main complication during CRRT was bleeding, transient hypothermia, thrombocytopenia and filter clotting which occurred in about one-third of the patients. CONCLUSIONS We conclude that CVVHDF may be an alternative method of renal support for critically ill children after cardiac surgery in experienced centers, but a significant number of specific complications should be taken into account.