In terms of the issues aggravation concerning internally displaced persons and the disproportions in the social and economic development of regions as a result of the antiterrorist operation in Ukraine, an analysis of social and economic transformations in regional development under the migration processes influence and the search for their overcoming mechanisms becomes relevant. The purpose of the article is to analyse the impact of internally displaced persons flows on the social and economic development of regions in order to improve the regional development mechanisms in Ukraine. The research methodology includes a set of scientific research methods that provide a systematic approach to investigating the impact of internally displaced persons on the social and economic development of Ukrainian regions, theoretical approaches to state regulation of internal migration flows in conditions of decentralization of power and reform of public administration in the country. In the course of investigations, the following methods are used: statistical analysis and synthesis while determining the indicators of the IDPs burden on the regional social and economic systems of Ukraine; analysis while studying the main problems of internally displaced persons and their directions; logical synthesis and synthesis while drawing conclusions. The information base for the study consists of the legislative acts of the Verkhovna Rada of Ukraine, the Decree of the Cabinet of Ministers of Ukraine, statistical and reporting information of the Ministry of Social Policy of Ukraine, development of the UN Agency for Refugees, the UN ReliefWeb Specialized Service for the Coordination of Humanitarian Affairs, Inter-Agency Standing Committee, PROMAN, NGO “Labor and Health Social Initiatives”, Ukrainian Helsinki Human Rights Union, research results of domestic and foreign scientists. Results. The article deals with the issues of effective reforming of regional development mechanisms related to solving the internally displaced persons’ issues and their impact on social and economic processes in the regions. The internally displaced persons’ influence analysis on the regional social and economic systems of Ukraine was conducted. The analysis allowed determining the rating of five regions with a significant load of IDPs and identifying the social and economic system in the region and the acutest elements. Practical implications. The peculiarities of internally displaced persons’ migratory flows by regions and their impact analysis on the social and economic development of regions and Ukraine as a whole are to be investigated. Value/originality. The ways of positive social and economic dynamics of regional development enhancement due to the programs and regional development strategies correction, taking into account the resource potential of the IDPs in some areas, are proposed.