Computer simulation is a cost-effective methodology to examine the results of alternative crop management practices on agricultural production, estimate the use efficiency of resources, and assess the sustainability of cropping systems. Confident use of simulation models depends on the continuous improvement of these tools and the adequate calibration to local conditions. The Decision Support System for Agrotechnology Transfer (DSSAT) is a simulation environment providing models for 25 crops. The newest version of DSSAT, version 4.5, gives users the opportunity to choose between two maize models, CSM-CERES, and CSM-IXIM a more mechanistic model. In this work we compare the simulations of crop growth and yield obtained with these crop models in two high yielding irrigated cropping systems of Mediterranean climate in Spain