Purpose: The purpose of the present study is to examine the impact of age, sex and body mass index (BMI) on some indices of the pulmonary ventilation in healthy children actively practicing sport, between 11 and 14 years of age, living in Plovdiv, Bulgaria. Materials and methods: A group of 22 healthy volunteers (boys, n=14 and girls, n=8) with high level physical activity underwent a functional test for the evaluation of pulmonary ventilation. In order to assess the influence of age, BMI and sex on some indices of pulmonary ventilation, they were divided into the following groups: in accordance with the age - group 11-12 years old (n=14) and group 13-14 years old (n=8); in accordance with the BMI group < 20 kg/m2 (n=14) and BMI group >20 kg/m2 (n=8) and in accordance with the sex – boys group (n=14) and girls group (n=8). The results are presented as X±SD. The data has been analyzed with Independent Samples Test (t-test) (SPSS v. 13. 0). The difference at P<0.05 was accepted as significant. Results: We did not find significant differences in most of the indices between the groups by age, body mass index and sex. Although there was higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys compared with the girls. Conclusion: Despite the good health condition and high level of physical activity, we found out higher maximum pulmonary ventilation and higher peak (maximal) expiratory flow in boys as compared with the girls.