The purpose of this study is to investigate comparative advantages of corn in comparison with other competitor crops. To do so, Linear Programming, to 2004-2005 data related to classic index (DRC) in Kermanshah province was applied. Results showed that corn has comparative advantages in all regions of Kermanshah province while in optimal cultivation pattern of 37.5 percentages of regions in existence of rotation and 50 percentages of regions in lack of rotation, corn acreage has been increased. In addition, comparing optimal cultivation pattern resulted from linear programming models with crops ranking based on comparative advantage indices indicated that, resources availability and limitations, tradable and non-tradable inputs costs and yield will lead to shift in production’s comparative advantage from one crop to another. Factors such as supporting policies and rotation might also have effects on comparative advantages and optimal cultivating pattern.