The structure of the work – as indicated earlier – is based on solving the research problem posed. It results from the adopted goals and formulated research hypotheses. The need to analyse the above issues related to the research area was included in the structure of the thesis, divided into four chapters. The first chapter is devoted to the issues of micro, small and medium-sized enterprises. It presents key definitions and classifications based on the existing legal framework in Poland. A statistical review of SMEs was conducted and the role of this sector of enterprises in the national economy was shown. Moreover, the European Union's policy towards micro, small and mediumsized enterprises was also reviewed and the main determinants of their development were presented in the light of the quoted research. The second chapter concerns the issue of business environment institutions. It reviews the most important concepts, presents the division of business environment institutions by form of support; analyses the organizational and legal aspects related to the functioning of BEI, also the spatial distribution of the discussed institutions indicating what role they play and the directions of their further development. The third chapter analyses the activities of business environment institutions in the area of financial support for micro, small and medium-sized enterprises. The analysis included the activities of loan funds, guarantee funds, business angel networks and private equity/venture capital funds on the Polish market. The fourth chapter of the paper concerns the analysis of the functioning of business environment institutions in the field of financing support on the basis of research conducted among micro, small and medium-sized enterprises in Poland. It presents the methodology of the research, characterizes the research sample and analyses the results obtained. The results of the study were also the final conclusions along with the evaluation of the functioning of financial BEIs and the author's recommendations for future activities for the analysed institutions. The literature in the form of scientific monographs and articles in peerreviewed scientific journals was used to write the study. In addition, legal acts, reports and analyses, internet sources and the author's own research and analysis were also used.