The paper deals with the implementation of security measures in small to medium developing countries. Based on Croatian experience, it examines possibilities for efficiently combining security measures that should be implemented in SOLAS ships and ISPS compliant ports with those appropriate to non-SOLAS ships and ports where measures defined in the ISPS Code are not mandatory. Finally, it examines measures promoting a more extensive use of information technologies, particularly information fusion and dedicated decision support systems, in order to enhance the level of maritime security and protection from illegal activities at sea and in ports.