Public procurement as a system of procedures for purchasing goods and services is quite complex. Especially having in mind international legal regulation and high requirements for the assurance of such principles as transparency, fair competition, non-discrimination, mutual recognition, proportionality. Thus from the other side of the issue, in special fields as defence and national security, it is not always possible to strictly observe the mentioned rules. Institutions in a state, which is facing threats, must be able to flexibly; this would allow balancing the urgency and competiveness of purchasing procedures. Still such situations require clear managing system and legal regulation supporting it. In this article, the authors present the preliminary analysis of management of public procurement for defence and security via disaster management cycle theory and mostly focus on the phase of response towards certain destructive actions. The managerial aspect of the issue is supplemented by the analysis of the legal regulation, which should support managerial processes. Having in mind that in different phases of the disaster management cycle, different methods of management (requiring special legal regulation, as legitimation of such actions) should be applied, examples of two countries are presented. Lithuania as a member state of European Union is chosen to illustrate the reflections of managerial processes in legal acts, which are passed in the phases of mitigation and preparedness. Ukrainian example is presented to illustrate the difficulties, which state may face, when managerial processes as well as legitimation thereof in legal regulations are developed in the phase of response. To answer these questions, literature review, comparison, analyses of documents, synthesis and other methods were used. It is concluded that the public procurement processes definitely should be prepared in advance and every state should be ready for the urgent purchases before the direct threats for security appears. Ukrainian example shows, how it is difficult, costly and requiring other efforts to develop these processes and implement it in the same time. It should be mentioned that raised questions are in the constant process of learning and this article should be considered as a primary steps towards deep analysis of the continuity of state actions in the situations of real threats and tensions, which Europe is facing today.