The aim of this study was to investigate the effect of a sort-term walking exercise on some lung function parameters (such as forced vital capacity (FVC) and maximal voluntary ventilation (MVV)) in obese children. Total of 23 subjects who have BMI (body mass index) > 25 kg/m² and age ranged from 12 to 14 years participated in this study. Subjects were randomly divided into two groups as intervention (n = 12) and control group (n = 11). Anthropometric features of subjects were shown in Table 1. For this study, lung function parameters were measured by using a spirometer. In this research, throughout 6 weeks, participants followed a closely supervised walking program consisted of 45-min sessions five times in each week with an intensity of 60% of heart rate reserve. SPSS was used for statistical analyses (SPSS Inc., Chicago, IL). T tests were utilised to compare before and after the changes between groups. Table 2 shows that there were significant increases in FVC and maximum MVV (p < 0.05) in intervention group. Although before the study the mean baseline FVC was 2.99 ± 0, 50 litres (L), this value changed to 3,09 ± 0,51(L) after the 6-week walking period. Further, MVV values of post-training period were significantly higher than that of pre-training period (111.73 ± 21.99 vs. 115.21 ± 18.99; Pre-training vs. Post-training. p < 0.05). Control group had no significant change in all outcomes from pretest to posttest (p > 0.05). All in all, short-term walking program had a significant positive effect on FVC and MVV lung functions. This research was designed to specify the effect of walking on respiratory system. The result of this study indicated that a short-term moderate intensity walking exercise may enhance changes in obese children’s respiratory system.