A study was carried out in 200 school children from north India to find out the effects of passive smoking and exposure to domestic cooking fuels on their lung functions. Forced vital capacity and FEV1 were the lowest in boys whose households used biomass fuel (p < 0.05) and PEFR and FEF 25% and 50% were lowest in boys with their homes using kerosene as fuels. All these were the best for LPG fuel. However, in girls there was no significant difference in different parameters, although the values were lower in those using kerosene and biomass fuel. All parameters were lower in passive smokers irrespective of the type of fuel used although they were not statistically significant. However, FEF 50% was significantly less in passive smokers whose households used mixed fuels. The same was true for PEFR, PEFR %, and FEF 25% in cases of LPG fuel use.