This ecological time series study aimed to evaluate the effects of air pollution on hospital admission from respiratory diseases, considering differential susceptibility according to age, of the Volta Redonda citizens, Brazil, from January 2002 to December 2006. This period was chosen to define basics parameters to assess the impact of national policy Environmental Health Surveillance related to Air Quality. This epidemiological design using daily data on hospital admission for respiratory diseases for the total population, the elderly, and children. Daily levels of PM10, SO2 and O3, minimum temperature and relative humidity were also analyzed. Generalized Additive Models was fitted to Poisson regression analysis. The results showed the increase in risk of hospital admission from PM10 was 2.67% (95% CI: 0.40 – 5.00%) in the total population, 4.15% (95% CI: 0.17 – 8.29%) in elderly and 5.22% (95% CI: 0.14 – 10.56%) in children. For exposure to SO2, only the total population showed increased risk 6.59% (95% CI: 0.76 - 12.71%). The risk wasn´t significant for O3. These results reinforce the need for additional studies, focusing on effect modification of air pollution on human health, considering not only the stratification by age but also others susceptibility factors.