Inter-child variability in breathing patterns may contribute to variability in fine particle, lung deposition and morbidity in children associated with those particles. Fractional deposition (DF) of fine particles (2um monodisperse, carnauba wax particles) was measured in healthy children, age 6-13 (n=36) while they followed a resting, breathing pattern previously determined by respiratory inductance plethysmography. Inter-child variation in DF, measured by photometry at the mouth, was most strongly predicted by their tidal volume (Vt) (r =0.79, p<.001). Multiple regression analysis further showed that for any given height and age, Vt increased with increasing body mass index (BMI) (p<0.001). The overweight children (95^th percentile BMI) (n=8) had twice the DF of those in the lowest BMI quartile (<25^th percentile) (n=9), 0.28±0.13 vs. 0.15±0.06 respectively, p<0.02. In the same groups, resting minute ventilation (Ve) was also significantly higher in the overweight children, Ve = 8.5 ± 2.2 vs. 5.9±1.1 L/min, p < 0.01. Consequently, the rate of deposition, Drate (i.e. particles depositing/time), in the overweight children was 2.8 times that of the leanest children (p<0.02). Among all children, Drate was significantly correlated with BMI (r=0.46, p=0.004). These results suggest increased weight in children may be associated with increased risk from inhalation of pollutant particles in ambient air.