Introduction: Tobacco smoke is one of the most important environmental pollutants (ETS). Passive exposure to tobacco smoke is involuntary and it presents a health risk for children. Objective: To establish if there are differences in Peak Expiratory Flow Rates (PEF) values of healthy school children who live in households with and without tobacco smoke. Methods: PEF measurements were taken for 830 school children, from elementary schools in Nis and Laplje Selo. Mesurements were obtained with new peakflowmetars Vitalograf-normal range (EN 13826), 3 to 5 times. The higest values were taken for analysis. P < 0.05 was considered significant. Results: We considered PEF values for 830 healthy school children, 599 (72.17%) from households with tobacco smoke (ETS), and 231 (27.83%) without ETS. Exposure to parenteral smoking was associated with reduced PEF rates: 312.01 L/min (95% CI=301.38-322.65 L/min), for boys and 284.64 L/min (95% CI=275.73-293.55 L/min), for girls. PEF rates for children from households without ETS are 313.79 L/min (95% CI=295.63-331.93 L/min) for boys, and 302.0 L/min (95% CI=287.02- 316.98 L/min) for girls. PEF rates were significantly lower for girls from households with ETS (p<0.05). Boys, with and without ETS, had no statistically significant differences between their height, weight and age, so their PEF rates could be compared by their absolute values. For girls, this was not the case, and after age, height and weight adjustments their PEF rates showed no statistical significance (p= 0,346). Conclusions: Parental and household smoking were associated with decreased lung function in school age children. Although it's possible to reduce exposure to tobacco smoke in public places, it's important to inform parents about longterm impact of tobacco smoke on the health of their children.