Introduction. Obesity is associated with a rapid decrease in ventilatory function. The most common way of assessing nutritional status and measuring abdominal fat and hips are the body mass index (BMI) and the waist-hip ratio (WHR).Thereisscarceevidencesuggestingtheir relation to functional residual capacity (FRC). Our objective was to determine the relation among BMI, WHR, and FRC in obese children in the city of Talca, Chile. Population and methods. Male and female children were recruited (6-12 years). Weight, height,BMI,WHR,andpulmonaryfunctionwere assessed;thelatterwithbodyplethysmography. Depending on data distribution, Student’s t test or the Mann-Whitney U test were used for independent samples, while Pearson’s or Spearman’s r test was used to establish the correlation between WHR and FRC. Results. Children were divided into normal weight (n = 18) and obese (n = 18). A significant reduction in FRC (p = 0.025) was reported in obese children, while a reverse association was observed between WHR and FRC, which was moderate in normal weight children (s = -0.489; p = 0.03) and high in obese children (r = -0.681; p = 0.001). Conclusions.ObesechildrenshowedalowerFRC compared to normal weight children, which, in turn, was associated with WHR. These results are indicative of the systemic effects caused by obesity on children’s ventilatory function and the need to use body fat distribution indicators at an early age.