The work deals with the concept of Schengen as one of the greatest successes of the European Union, describes the facilitated free movement within the borders of the European Union, the right to life, education, work and pension anywhere in the EU, but also the extreme risks that are threat to the national security of the member states, and solutions and protocols in dealing with the emergence of these problems, such as, for example, increased control at the external and internal borders of the European Union, and the work and actions of institutions that deal with raising the level of general security throughout the EU. Also, it describe the differences between the European and national Schengen legal frameworks, visa policy, migration and asylum policy, as well as the conditions for the entry of EU member states into the Schengen area. The paper describes the process of entrying of Republic of Croatia to the Schengen area through extensive and demanding evaluations, and technical recommendations that Republic of Croatia had to fulfill before entering the Schengen area. The treatment of citizens of third countries is explained, with the help of various legal documents that are used by the EU institutions, the judiciary, and the border police in the daily problem of the increased influx of illegal imigrants. The accession to Schengen and the introduction of the European concept of integrated border management strengthened the reputation and role of the Republic of Croatia.