CPSI – Changing Perceptions on Security and Interventions – is a multinational research project funded by the 7th Framework Programme of the European Union, under the 1st Security Research Call ("Security and Society") 2007. The goal of the project is to provide governments and related organizations with a methodology to increase insight into the determinants of actual and perceived security, and into which interventions are effective for increasing security. The deliverables of this project represent practical and ready-to-use tools, which can be employed by policy makers and other end-users to formulate policy regarding security. In this project we will develop 1) a conceptual model of actual and perceived security and their determinants, 2) a methodology to collect, quantify, organize, analyse and interpret security-related data, 3) a data warehouse to store and extract for analysis data amassed using the methodology, and 4) carry out a validation study to test the model, methodology and data warehouse. We will test if it is possible to answer relevant security-related questions from the field using the methodology. The project deliverables can be used by end-users to assess security at the international, national and local levels and to draw conclusions regarding such issues as: What are the levels of actual and perceived security in specific locations?, Which interventions work where?, and Which interventions should be implemented in which locations?