The article is dedicated to the analysis of China’s and Ukraine policies as challenges at the beginning of the XXI century. External and internal factors which influence the NATO’s definition of its role and place in the contemporary system of international relations are considered. To this purpose, the content of certain definitions, specifics of internal development of Western society of the second half of the XXth century which form subsequent perception of security environment as well as the impact of China and Ukraine on the NANO’s choice of the ways of adaptation to the contemporary security processes. The author notes that China and Ukraine are substantially different challenges for NATO and initial analysis shows that the Alliance rather quick and promptly takes into account their meaning for the creation of adaptive mechanisms and instruments to the contemporary world political processes. China’s challenge makes NATO to activate the process of its “globalizing” through the creation and participation in supplementary security mechanisms and institutions beyond the Statute’s defined Euro-Atlantic region. At the same time, Ukraine acts as an outpost of Western word covering the Alliance’s members from Russian aggression and giving them possibility to make rearmament necessary for efficient rebuff in case of attack. Ukraine’s challenge lies in that NATO support of Kyiv increases the risk of direct military collision between NATO and the Russian Federation.