The author analyses the manifestations of cities’ growing role for ensuring the national/international as well as environmental and human security. Cities of today increasingly participate in international relations – they internalize, implement and enforce international law, sometimes independently of their States’ international legal obligations, for example when they pledge to implement human rights conventions or environmental law obligations that their own States did not pledge to fulfill. In this way they contribute to international peace and security. On the basis of those manifestations, the author attempts to explain the possible position of cities on the international plane and according to international law – whether they should be accorded greater autonomy or international legal personality. The author also indicates that the role of cities in the area of different aspects of security is growing.