The article deals with the results of a comparative legal analysis of adoption legislation in France, Great Britain, Russia, Spain, Germany, Italy and the USA. The analysis includes the following components: requirements for adopters (or an adopter), types of national adoption, persons giving their consent to adoption, requirements for a child, special requirements for adoption, impossibility of adoption, adoption outcome, relationship between an adopter and an adoptee before adoption, adoption privacy, adoption cancellation, relationship between an adoptee and his or her former family. The object of this research is the adoption legislation in different countries. The authors used both general scientific methods such as analysis, deduction and classification, and a specific scientific method - the comparative legal method for studying adoption, which has oriented the research on the specific result - to determine a possibility of unification and harmonization of the national adoption legislations. The article deals with a number of tasks: to show the development tendencies of the adoption institute; to determine the general and specific development regularities of the national adoption systems. The content of the research includes the following results: 1. Most of the countries have common universal principles: taking the child's interest into account, receiving the interested persons' consent to adoption and giving married couples priority in adoption. The established practice was conditioned by the expansion of the "intercountry adoption" institution, which divided countries into those which "receive" and "give" children. The practice required unification of some adoption procedures by adopting a number of international instruments. A distinctive feature of such instruments is in the fact that much is left at the discretion of the participating countries. Accordingly, domestic legal systems of adoption still dominate in those countries. 2. At present, a more complete unification of the legislation is unlikely due to the chain of institutions already functioning and the current regulations interwoven into the existing legal system, rather than some traditional cultural practices of the countries. Thus, the unification of the adoption institution, which can promote the effectiveness of "intercountry adoption," is unlikely. International legislation will mostly be represented by bilateral agreements and regional acts in the best interests of all parties. 3. Modern foreign legislation is characterized by the complexity of adoption procedures (i.e., living with an adoptee before adoption, spouses living together for a long time, expansion of the list of persons giving their consent to adoption), which guarantees additional protection of adoptees' and adopters' rights. 4. In foreign legislative practice, there is a divergence of opinion regarding advantages and disadvantages of open adoption, which allows to keep a relationship with a former family as it is accepted in the USA and France.