Abstract: The paper studies the peculiarities of Russia’s economic relations with the countries of Eastern Europe under western sanctions. The research object is Russia’s economic relations with East European countries. The research subject covers the dangers and the threats to Russia’s economic security connected with bilateral economic relations with former countries of the Council for Mutual Economic Assistance in historical retrospective and at the modern stage. The authors analyze the development of economic relations between Russia and the mentioned countries with account for the current geopolitical and geo-economic situation, which includes the interests of joint economic activities of parties to the relations. The topicality of the study consists in the ambiguous character of development of the peculiarities of economic relations between Russia and the new EU member-states in the context of the new geo-economic balance of powers, toughening of international competition and the increased volatility of European markets. The proposed research method includes the historical approach, political and economic analysis of scientific sources, official media reports, and statistical data describing the dynamics of economic relations between Russia and the countries-founders of the CMEA, and the comparative analysis of actions of the parties to bilateral relations in the context of political transformations in Eastern Europe and anti-Russian sanctions. The authors conclude that the toughening of international competition in Eastern Europe is still threatening national security of Russia, but with account of easing western sanctions against Russia, there are tendencies of positive development of bilateral economic relations. Besides, to consistently implement the initiatives of Russia and East European countries, it is necessary to scientifically reason the instruments of investment promotion and business activities encouragement. The research results can serve as the information and analytical material for politicians, diplomats, specialists of international relations studying economic aspects of Russia’s relations with new members of the EU.