Background: As a result of an imbalance between energy intake and expenditure in the population, obesity is currently a problem in the developed countries. The increasing incidence is observed both in adults and children. Aim of this study: to evaluate the changes in nutritional state and cardiovascular system parameters during a stay in Childrens Treatment Centre. Methods: Children were observed for one month (n=49; age 8-17 years; 27 girls). All the measurements were made at the beginning of the stay (in)and its end (ex), and include nutritional state parameters (weight, height, body mass index - BMI, waist to hip ratio - WHR, overall fat ratio % fat, basic metabolic expenditure - BME; Inbody system, USA) and cardiovascular system parameters (systolic and diastolic blood pressures - SBP, DBP, pulse interval - PI). Cardiovascular parameters were obtained from 5 minute continuous BP measurement using non-invasive Penaz method (Finometr, FMS, Netherlands). Then, spectral analysis was employed for estimation of baroreflex sensitivity (BRS) as a parameter of short-term BP regulation. A Wilcoxon paired test was used for statistical analysis. Results: During the stay, nutritional state parameters decreased significantly (p<0,01); in versus ex: weight 77,6±16,3 vs. 72,7±15,4 kg;BMI 29,2±4,0 vs. 27,2±3,6 kg/m2;% of fat 38,2±7,2 vs. 35,4±7,7%; WHR 0,94±0,1 vs. 0,92±0,1; BME 1415,1±243,7 vs. 1392,4±233,6 kcal. In cardiovascular parameters statistically significant (p<0,05) increase in PI (743,0±120,8 vs. 813,0±126,6 ms) and BRS (8,5±3,6 vs. 10,5±4,7 ms/mmHg) were observed. were observed. Conclusion: This study shows the positive effect of the stay of children with diagnosed alimentary obesity in Children´s Treatment Centre both on the cardiovascular system function (improved control by parasympathetic nervous system) and on nutritional parameters.