Aims: In this study, the health impacts of SO2 in three cities, including Ahvaz, Kermanshah and Boushehr was quantified and compared based on modeling using data from Department of Environment (DoE) in 2011. Materials and Methods: Required data were collected from DoE and Meteorological Organization. Later, data were processed by Excel software and entered into AirQ Model; this model is identified by the World Health Organization. The processes include: Correction of temperature and pressure, matching the unit with the model. Results: Results from three study areas showed that SO 2 concentration in Kermanshah city with the annual average of 103 μg/m 3 and in Boushehr city with 44 μg/m 3 was the highest and lowest in 2011, respectively. In all three cities, 8% and 1% increase in risk of cardiovascular and respiratory mortality was observed, respectively, per 10 μg/m 3 increased in concentration of SO 2 . Conclusion: About 60% of cardiovascular deaths attributed to SO 2 in ambient air of Ahvaz occurred in days with pollutant not exceeding 90 μg/m 3 , whereas 46% and 41% of this health end point occurred in days with sulfur dioxide concentration not exceeding 190 μg/m 3 and 100 μg/m 3 in ambient air of Kermanshah and Boushehr, respectively. In comparison, Kermanshah and Boushehr were the highest and lowest in view of cardiovascular and respiratory mortality attributed to SO 2 concentration in 2011, respectively.