Introduction: populist rhetoric accompanying the concept of “child’s interest” gained its doctrinal tradition almost immediately with the adoption of the current Family Code of the Russian Federation. Regardless of the purpose of interpretation of this concept, its essence is usually reduced to the subjective aspirations of the child, which must be considered by all his social environment. As the textual analysis of the norms of the RF Family Code and the practice of law enforcement shows, the accumulation of experience of inconsistent and synonymous use of the concepts of “child’s interest” without a doctrinal analysis of the concepts related to it – legitimate interest, legally protected interest, and sometimes replaced by it, continues. Not without this, the question of how legal and non-legal relate in this concept remains open and not a little attracts the attention of the doctrine, although science still sends signals about the need for more “fine-tuning”. The purpose of the study is to theoretically recognize these signals using theoretical and methodological tools in order to conduct a theoretical categorization of the legal concepts “interests of the child”, “legitimate interests of the child”, “protected rights and interests of the child” that are actively used in the doctrine of family law and are very inconsistent in legislation. Methods: general scientific (dialectical); private scientific methods of cognition: formallegal, logical. Results: the structure of scientific knowledge about the interests of the child is not obvious today. In many ways, this state is generated by the facts of arbitrary use of interesting terminology. Family law science in this part does not so much create new scientific knowledge, but rather reflects the actual state of Affairs. While the real connection of the concept of child interest with legal matter implies not so much the frequency of its use in family legislation, but rather the connection with objective criteria. Based on the results of the study, the authors came to the following conclusions. One of the possible ways of further legally oriented research of the child’s interests may be to change the existing theoretical positions by attracting arguments based on the principles of regulatory and protective law. It appears to the authors, this approach will be able to distinguish between the interests of the child are significant for the implementation of its legal (legitimate interests) and interests, which in the case of a breach, to restore, to return the child the welfare state, which guaranteed to him by international and domestic law for the purposes of the full development of his personality (interests protected by law).