This paper aims to identify the types of financing structures of the economy that exist in European Union countries highlighting the features of each structure. For each type of financing system of the economy identified we observe the financial resources available to companies. Depending on these we identify how there are financed the companies in each market, more exactly what capital structure do they have, and moreover what is the optimal capital structure in each case. So, by this analysis, we want to see if the financing system of an economy influences the optimal structure of the companies operating in the capital market from that country. In various stages of development of the financial system, the company financing depends on the general characteristics of the environment in which the enterprise operates. The financing system existing in a country plays an important role on the capital structure of an enterprise because according to the specific of each country the enterprises have access to more or fewer financial resources. We also analyze the supply of financial resources within each system, exactly the actual money that businesses can have on those markets and key management decisions on enterprises financing. In this paper we combine the theoretical analysis with the empirical results obtained by the studies realized by European Commission. It is important to keep in mind that the results obtained by the analysis realized in the last years may be influenced by the manifestation of the global financial crisis. An important result of this analyze is that the external environment and the disturbances in the external environment have a significant influence on the financing of businesses operating in a country. This was proved again by the impact of the current financial crisis on the activities of the enterprises on each market from European Union.