This paper presents the protection of the rights of one of the most vulnerable groups in society - children, the protection of whose rights began and intensified during the 20th century. At the international level, the emphasis is on the United Nations Convention on the Rights of the Child as the most important convention for the protection of children's rights and on its three optional protocols. The presentation of the regional protection of children's rights within the framework of the European area is given, due to the fact, that the Republic of Croatia is a member of the European Union and a member of the Council of Europe, which adopted the Convention for Protection of Human Rights and Fundamental Freedoms, as one of the most significant conventions for the protection of human rights in Europe, then the European Social Charter, but also a whole series of contracts that deal with specific issues of protection of children's rights. The final part of the paper talks about how the rights of children are protected in the legal system of the Republic of Croatia, mainly through the provisions of regulations and the activities of the Children's Ombudsman, as a special institution for the protection of children's rights.