Steam power plants using heavy oil provided about 17.4%, equivalent to 35.49 TWh, of electricity in Iran in 2007. However, having 1.55-3.5 weight percentage of sulfur, heavy oil produces SO2 pollutant. Utilization of Flue Gas Desulfurization systems (FGD) in Iran's steam power plants is not common and thereby, this pollutant is dispersed in the atmosphere easily. In 2007, the average emission factor of SO2 pollutant for steam power plants was 15.27 g/kWh, which means regarding the amount of electricity generated by steam power plants using heavy oil, 541,000 Mg of this pollutant was produced. In this study, mass distribution of SO2 in terms of Mg/yr is considered and dispersion of this pollutant in each of the 16 steam power plants under study is modeled using Atmospheric Dispersion Modeling System (ADMS). Details of this study are demonstrated using Geographical Information System (GIS) software, ArcGIS. Finally, the average emission factor of SO2 and the emission of it in Iran's steam power plants as well as SO2 emission reduction programs of this country are compared with their alternatives in Turkey and China. (C) 2012 Elsevier Ltd. All rights reserved.