OBJECTIVE To determine reference values for cystatin C (CysC) and its correlation with creatinine (Cr), gestational age, birthweight and maternal Cr status in very low-birthweight (VLBW) preterm infants. METHODS The study included 113 VLBW premature infants (<1500 g) of ≤ 32 gestational week. Serum Cr and CysC of the infant and serum Cr of the mother were analysed. RESULTS The mean level of CysC was 1.77 ± 0.38 mg/L on day 1 and 1.61 ± 0.37 mg/L on day 3, and the decrease was statistically significant. There was a significant correlation only between maternal Cr and first-day Cr values and negative correlations between Cr and gestational age and birthweight on third day. Creatinine was not correlated with CysC both on day 1 (r = -0.077, p = 0.417) and day 3 (r = 0.132, p = 0.164). CONCLUSIONS Here, we report the reference ranges for CysC and Cr on first and third day in VLBW infants. CysC concentrations significantly decrease by day 3 compared with day 1 and are independent of gestational week, birthweight and maternal renal function status in VLBW preterm infants.