ENThe relevance of this study. In today’s society, a phenomenon like the different names of family members living together in a family is found quite often. Recently, there has even been an increase in such a phenomenon. This is influenced by the growing number of divorces, as well as the growing trend towards cohabitation relationships and the growing number of children born in such relationships. The main problem. Due to different surnames, there are more and more problems such as confusion in training, health and other institutions, as well as, inevitably, problems when traveling. Also, when experiencing difficulties in maintaining a relationship with the family, the child may not understand why his or her last name should be different from the parent’s last name, resulting in feeling excluded, outside of the family, experiencing bullying, or other similar difficulties. The aim of this study is to reveal the problems of legal regulation of different parents’ and their children’s surnames in the practice of Lithuanian courts. The following tasks were set for the defined goal: To reveal the concept of the child’s rights and legitimate interests in the surname, as well as to discuss the development of the regulation of the surname, the main functions of the surname in society; To analyse the peculiarities of the legal regulation in Lithuania related to the child’s surname; To analyse the practice of Lithuanian courts in cases regarding the change of a child’s surname.The paper concluded that Lithuanian courts do not avoid errors and misinterpretations related to the child’s rights and legitimate interests in the surname. The most equitable option in cases of changing the surname of a minor child, which best safeguards the child’s rights and legitimate interests, could be to change the child’s surname to a double surname consisting of different parents’ surnames, reflecting the relationship with both father and mother. The novelty In Lithuania, there are very few studies related to the possible violation of children’s rights and / or legitimate interests due to the different names of parents and their children, therefore it was expedient to perform a deeper analysis of the problem and make suggestions that can help solve the problem. As the result the fairest solution is to give the child a surname that indicates both the mother’s and father’s relationship to the child. Theused methodology is scientific literature analysis, descriptive, analytical, comparative, and logical methods. Key words: different surnames of parents and their children, child’s rights and legitimate interests, family law. [From the publication]