This report reviews the EU Directive’s guidelines for a model’s quality assessment, and examines specific model quality criteria, that may be used for model accuracy assessment according to the intentions of the EU directives. Several model accuracy measures are tested utilizing a one-year simulation with the chemical transport model REM-CALGRID (RCG). RCG was applied in the regional scale mode, covering Europe with a resolution of about 25*25 km2 for the entire year 2002. The model simulation results were compared with the data from about 300 - 400 measurement sites of the German air quality network.