The institute of adoption is a complex legal institute with a thousand-year-old tradition dating back to the pre-Roman period. Following the development of this institute, we can also follow the development of social relations from the very beginnings of humanity until today. Roman law recognizes two basic forms of adoption, as legal ways of coming under paternal authority - adoption and arrogance, while modern Croatian law regulates a unique form of adoption. Throughout history, adoption has had various goals: from strengthening tribes, continuation of the family, inheritance, improving the status of illegitimate children or liberation from slavery, to protecting the interests of children, the right to parental care and the right to parenthood. The institution of adoption has been known since the Code of Hammurabi and perfected in Roman law, whose foundations we also recognize in contemporary Croatian law. Although the adoption of Roman and modern Croatian law have certain common points, the motive is still different, which is caused by complex social changes. The thesis provides an overview of the development of the institute in the pre - Roman period, an analysis of the legal regulation of the institute of adoption according to Roman law and a comparison of the institute of adoption of Roman and modern Croatian law.