A comparison of accuracy between electrical bioimpedance analysis (BIA) and body mass index (BMI) for fat mass evaluation in children was the aim of the study. One-hundred and ninety three healthy children (90 females, 103 males) were enrolled. The mean age of the studied population was 11.8 years (+/- 2.2), mean weight equalled to 42.6 (+/- 12.8) kg and mean height-151.1 (+/- 13.5) cm. BIA measurments were performed by multifrequency (1; 5; 50; 100 kHz) BIA 2000M analyzer using BIANOSTIC electrods. Calculations of free fat mass and fat mass were performed using Nutri 4 Data Input Software (Germany). The LMS method for percentile charts of FFM and FM acording to height has been applied and results for boys and girls were drawn separatelly. Percentile charts of FM and BMI were compared. Different shape of curves of FM content and BMI for boys during puberty was noticed. BIA allows for precise fat mass content evaluation in children and its use should be disseminated.