The purpose of this thesis paper is to show the importance of the institution of adoption with an international element, which is a relatively new form of adoption in the world in general. The paper showed the necessity to protect the child's best interest and the importance of preserving the child's benefits. After a historical analysis of the institution of adoption, legal systems of the countries of the world are highlighted, with the aim of highlighting the many differences between the legal systems. Precisely because of these differences of legal systems of some countries, there is a development of the institute of international adoptions, which are processed bellow the graduate thesis. It sets out the facts in the case of adoption croatian citizen by foreign adoptive parents. Also, there is a list of the cases in which croatian adoptive parents initiate procedure of adoption of foreign nationals. But, it is necessary to fulfill the assumptions of the Croatian Citizenship Act in order to perform international adoption. Also is analyzed the Hague Convention on protection of children and cooperation in international adoption, which was adopted 29. 5. 1993. Namely, its aim is to encourage the development of foreign adoptions, and to encourage international co-operation. It is necessary to create a stronger system control and prevent illegal adoptions during the establishment of international adoptions. Adoption with an international element should be carried out only if it is in the child's best interest.