The paper presents the results of the study of international and national cooperation of Ukrainian scientists from different scientific fields using citation analysis data from Scopus in the period of 2011-2015. The results show that during the period under study, the number of documents of highly cited Ukrainian scientists that have received enough citations to be included to the top 1%, 5% and 10% most cited documents in the world, evidenced an increase and were significantly different in different subjects areas. Papers written by a group of co-authors predominate among highly cited documents of Ukrainian scientists. Consequently, international cooperation plays an important role in Ukrainian scientists research results visibility and impact. At the same time, up to 16%-27% highly cited articles of Ukrainian scientists have been written without partnering with foreign colleagues, that means a significant part of important scientific results in Ukraine are carried out by oneself. Therefore, for generating an optimal policy of science development in Ukraine it is important to provide a balanced view of the expectations of the results of the international cooperation of Ukrainian scientists and achieving a required balance between the inter-country and international collaboration.