OBJECTIVES: .  The exposure to biofuel smoke is a risk factor for Chronic Obstructive Pulmonary Disease –COPD- while using natural gas may be protective against it. There is few evidence from Latin America on the relationship between use of different types of fuels to cook and respiratory diseases. The present report is aimed to assess differences in the prevalence of abnormalities to respiratory functions between populations who used biomass fuel to cook against those using cleaner sources of energy such as natural gas.   METHODS: A cross-sectional population based study was designed to evaluate the respiratory function, through spirometry, in subjects cooking with biomass or natural gas. All patients were evaluated by a general physician and a pulmonologist. We compared the prevalence of spirometry abnormalities on those cooking with natural gas versus those cooking with biomass fuel. A multivariable logistic regression was used to adjust differences by potential confounding factors. RESULTS: Overall 203 persons were studied. After adjusting by potential confounders there were a significant increase in the prevalence of severe obstructive pattern (OR 5.50; 95% CI 1.17-25.79) in subjects who cook with biomass compared with natural gas users. Values of Forced Expired Volume in one second (FEV1) and forced vital capacity (FVC) were lower among those cooking with biomass.  The differences in prevalence of respiratory morbidity and symptoms were not statistically significant between both groups. CONCLUSIONS: These findings suggest that replacing biomass fuel by natural gas may be an important public health intervention in Colombia because it can reduce the prevalence of abnormal patterns of pulmonary function.