The United Nations is an international organization and subject of an international law which primary objective is to maintain peace and security in the world, the development of good neighborly relations and economic cooperation, expansion of tolerance and promotion of respect for human rights and fundamental freedoms. Membership in the Organization, in accordance with the Charter of the United Nations, “is open to all peace-loving States that accept the obligations contained in the United Nations Charter and, in the judgment of the Organization, are able to carry out these obligations”. States are admitted to membership in the United Nations by decision of the General Assembly upon the recommendation of the Security Council. UN currently has 193 member states. The specialized agencies of the UN are the international organizations that are established by agreements between countries that have established relationships with the UN and have extensive responsibilities in the economic, social, cultural and other fields. Those are autonomous organizations that are associated with the UN with special agreements. There are 15 of such institutions and they are the subject of this final work in the context of the subjects of international law.