Due to the complex chemistry involved in troposheric ozone formation, it is difficult to predict the impact of controlling ozone precursor emissions. For this reason, modeling has become an important tool to predict ozone levels under varying emission scenarios. In spite of the efforts focused on reducing pollutant emissions, ground-level ozone concentrations in Spain are still exceeding thresholds established in EU legislation to protect human health and prevent damage to ecosystems. Resolution plays a significant role in modeling, especially when trying to simulate local effects. Higher resolution allows a more accurate definition of air pollutant transport pathways, although higher computing time is required. Besides the better definition of pollutants transport, a better model performance is also expected when simulating higher resolution domains. In this paper model predictions for three different resolutions have been analyzed over some areas in Spain (Madrid, Valencia and Pais Vasco) for 2004. Simulations of photochemical compounds were carried out using the regional V200603par-rc1 version of the CHIMERE model. A comparison between hourly model predictions and observations was done for O3 and NO2 in 2004. An improvement of ozone predictions was found for Madrid and Valencia areas when considering a higher resolution. The improvement of model predictions is more clearly observed for NO2 in this two areas. In the Pais Vasco area this improvement is not observed.