The Concept of international competition activities of the National Center “Junior academy of sciences of Ukraine” is presented. It is aimed at developing a system of selection, evaluation and training of Ukrainian students for their successful participation in international science fairs and other science and engineering competitions. In developing the Concept presented here (which can be considered a draft open for discussion and possible amendments), the authors used the international standards and their own experience in their participation in and organization of participation of Ukrainian students in national and international science fairs and other science and engineering competitions. The key provisions of the Concept are discussed, as well as its main components and aspects, such as: selection of international competitions for participation; national science fairs and other competitions and feeding fairs for international competitions; judging at the national competitions; evaluation of projects and selection of participants for the international level; national institutional coordination; the pre-competition training process for Ukrainian students, etc. The provisions of the Concepts form the basis for development of efficient educational programs for competitive selection, planning and implementation of various activities that will promote high-level achievements of gifted children and youth of Ukraine at the international/global level. Specific recommendations, rules and procedures for organizing participation of Ukrainian high school students in international science and engineering fairs and other competitions are outlined.