The report presents a brief description of the background, objective, accomplishment plan, status and present activities of the CEPA project JP 1.18 "Target and target-background modelling and validation for high resolution radar". Achieved results within the project during 2004 are presented in separate reports which are referred to in this report. Sweden (FOI) is the "leading nation" for this project. Both the technical and project management work has been a relatively demanding task during 2004. For codes based on physical approximations, which normally are required for large objects, the results often disagree with each other and with measurement results. The deviations are probably due to a mixture of programming errors and the physical approximations. In addition some codes lack options for e.g. handling non-metallic materials. The measurement results, which have been used as reference in the comparisons, have in general show good agreement with numerical calculations not based on physical approximations, e.g. method of moment.