Three genetic groups of pigs - Polish Large White, Polish Landrace and line 990 - were investigated for leptin concentration in blood, the expression of the leptin receptor gene in the hypothalamus, and the binding of leptin to its hypothalamic plasma membrane receptors. These parameters were correlated with average daily weight gain and fatness traits. Mean leptin concentration differed slightly between investigated groups. Unexpectedly, the lowest concentration of the hormone was observed in line 990 with the highest subcutaneous fat deposition. Simultaneously, higher mean concentrations of leptin in blood and an elevated mean leptin binding in the hypothalamus were characteristic for breeds demonstrating higher body weight gains (Polish Landrace and Polish Large White). On the other hand, the analysis of correlation did not show any interdependence for the investigated parameters within the groups. These results suggest that the amount of the fatty tissue is not the only factor responsible for leptin secretion and that the intensity of anabolic processes (measured as daily weight gain) is poorly correlated with the expression of hypothalamic receptors for this hormone in the pig.