INTRODUCTION:Obesity can cause deleterious effects on respiratory function and impair health and quality of life. OBJECTIVE: To evaluate the effects of obesity on the pulmonary function of adult women. METHODS: An obese group, constituted of 20 women between 20 and 35 years old with a BMI of 35 -49.99 kg/m 2 who were non-smokers and sedentary and had no lung disease were recruited. The non-obese group consisted of 20 women between 20 and 35 years old who were sedentary and non-smokers and had no lung disease and a body mass index between 18.5 and 24.99 kg/m 2 . Spirometry was performed in all subjects. The statistical analysis consisted of parametric or non-parametric tests, depending on the distribution of each variable, considering p < 0.05 to be statistically significant. RESULTS:The obese group presented a mean age of 25.85 ± 3.89 years and a mean BMI of 41.1 ± 3.46 kg/m 2 , and the non-obese group presented a mean age of 23.9 ± 2.97 years and a mean body mass index of 21.91 ± 1.81 kg/m 2 . There were no significant differences between the obese group and the non-obese group as to the age, vital capacity, tidal volume, forced vital capacity, and forced expiratory volume in one second. However, the obese group presented a greater inspiratory reserve volume (2.44 ± 0.47 L vs. 1.87 ± 0.42 L), a lower expiratory reserve volume (0.52 ± 0.32 L vs. 1.15 ± 0.32 L), and a maximal voluntary ventilation (108.5 ± 13.3 L/min vs. 122.6 ± 19.8 L/min) than the non-obese group, respectively. CONCLUSION: The alterations evidenced in the components of the vital capacity (inspiratory reserve volume and expiratory reserve volume) suggest damage to the chest mechanics caused by obesity. These factors probably contributed to a reduction of the maximal voluntary ventilation.