Assessment of glomerular filtration rate (GFR) is a useful way to assess renal function regardless of age. The gold standard is to measure GFR by isotope method, which in view of the considerable inconvenience for the patient and the high cost, is used only in special clinical situations. In clinical practice, the so-called estimated glomerular filtration rate (eGFR) is used, calculated from serum creatinine level based on one of the many available formulas. In adults, MDRD and Cockcroft-Gault formulas are the most common. In children the commonly used formula to estimate GFR is the Schwartz formula, calculation of which only requires the serum creatinine level and height of the child. The limitations of the methods are their lack of precision, especially in patients with normal or slightly reduced GFR. Recently, in the literature there appeared reports of alternative methods for calculating the estimated GFR. In this paper we compare different ways of calculating eGFR in children with normal or mildly impaired renal function. To calculate eGFR three models were used: the modified Schwartz formula, a new generalized quadratic model by Gao et al. and the height-independent model proposed by Pottel et al. The obtained values were compared with obtained values by glomerular filtration isotope method. The most similar results to the standard were in the group, in which eGFR was calculated by method of Gao et al.