Aim: The main aim of the study was to assess concentrations of neuropeptide Y, leptin and leptin receptor in teenagers treated for anorexia nervosa. Materials and methods: The study was conducted between 2007- 2011 in a group of 45 female teenagers with anorexia nervosa and a control group consisting of 59 healthy, regularly menstruating female age peers. Concentrations of leptin, leptin receptor, and neuropeptide Y (NPY) have been determined by using immunoenzymatic tests. Blood samples were obtained in fasting state. The Ethics Committee of the Medical University of Lodz approved of the study. Results: There were statistically significant differences between mean values of BMI (14.6 vs. 19.83), median value of leptin concentration (3.79 vs. 12.09), proportions of LEP/BMI (0.1986 vs. 0.5701) in the study group whe compared to controls. Higher values were found in the study group if compared to the percentage of body mass insufficiency - (23.09 vs. 3.91), neuropeptide Y concentration – (0.33 vs. 0.19), proportions of NPY/BMI – (0.023 vs. 0.0095), concentration of leptin receptor – (30.25 vs. 19.45), proportions of LR/BMI – (2.1048 vs. 0.9744). Conclusions: Low concentrations of leptine correlate to high concentrations of leptin receptor. A positive correlation between low body mass index and leptin receptor concentration and proportions of LR to BMI was found. A negative correlation was found between body mass loss and leptin concentration. The increasing concentration of neuropeptide Y, correlated to body mass defficency with existing high concentrations of leptin, could suggest disturbances of their regulatory axis.