Our study assessed the influence of mode of dialysis [continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD)] on residual renal function (RRF). The study retrospectively examined 30 children [15 on CAPD, mean age: 8.85 +/- 5.15 years; and 15 on APD, mean age: 10.17 +/- 3.63 years (nonsignificant)], followed for at least 12 months, for whom these methods were initial mode of treatment. Arterial hypertension was found in 80% of the children on CAPD and in 67% on APD. Parameters that were analyzed included 24-hour urine output; residual glomerular filtration rate (GFR); adequacy based on total weekly Kt/V urea and creatinine clearance; and hemoglobin, total protein, serum albumin, daily proteinuria, medications used, and causes of end-stage renal disease. After 12 months of decline in urine output, residual GFR was higher in children on APD (p = 0.06, nonsignificant). The difference in adequacy between CAPD and APD was nonsignificant, but a higher volume of dialysate was used in APD (p < 0.01). Proteinuria was present in 9 children on CAPD and in 6 on APD. In CAPD, we observed a negative correlation between the volume of dialysate and duration of treatment (p < 0.01, r = -0.79); in APD, a positive correlation (p < 0.0001, r = 0.89) was observed. In APD, we observed negative correlations between residual diuresis and duration of treatment (p < 0.0001, r = -0.9), serum albumin (p < 0.05, r = -0.6), and volume of dialysate (p < 0.001, r = -0.83). Residual renal function was better preserved in children with a glomerulopathy or a familial or hereditary renal disease than in those with pyelonephritis. Our results suggest that RRF is better preserved in children with a glomerulopathy or a familial or hereditary renal disease, especially in those treated with CAPD. Further studies are needed in larger groups of patients.