At present, obesity is considered one of the major health problems. It is a predisposing factor of several chronic diseases including non-insulin dependent diabetes mellitus (NIDDM) and coronary heart disease (CHD). Leptin levels in humans have been found to be highly correlated with total adiposity. We performed statistic analysis in order to identify linkage between leptin levels and anthropometric parameters in a group of 285 Czech obese children (152 girls and 133 boys) aged 7 to 18 years. The children were measured using the standard anthropometric technique according to Martin and Saller [16] at the beginning and end of a five-week therapeutic weight reduction programme. The skin fold thickness at 14 sites was assessed by means of Best calliper. The body composition was evaluated using Matiegka's technique. The leptin levels were investigated on the beginning and end of the reduction programme by direct enzyme linked immunosorbent assay (ELISA). For the evaluation of the grade of obesity, body weight, BMI (body mass index), RI (Rohrer's index), FMI (fat mass index) and normalized body weight, normalized BMI and RI were plotted. Correlation analysis shows relation between leptin concentration and FMI to be the most significant. As to ponderal indexes, normalized RI shows the most significant positive correlation. Leptin concentrations are negatively correlated with the proportion of the weight of skeletal muscles by Matiegka both in girls and boys. Intersexual differences in correlations between leptin concentrations and normalized circumferences are observed, as well as in correlations between leptin and particular skin fold thickness. We also tested relations between the magnitude of leptin decreases and magnitude of decreases of anthropometric parameters. There is a strong endorsement both in girls and boys of positive correlation between decrease of leptin concentration and fat reduction. Interestingly, differences between boys and girls in relations between leptin decrease and change in lean body mass had been observed.