Capital structure theory deals with the way in which firms finance themselves. There is no unifying theory on the choice between debt and equity. Current research does not point to a single capital structure theory that adequately explains capital structure choice mainly because there is a complex array of factors that influence enterprises owner-managers' financing decisions. The aim of the diploma thesis is to analyze the capital structure of a selected business entity with a subsequent proposal for its optimization. The analysis is carried out in two stages by means of selected financial ratios and then by analyzing the internal and external factors that influence the choice of an optimal capital structure for a given business entity. This chapter provides an overview of the various sources from where funds were procured for running a business. It also discusses the advantages and limitations of various sources and points out the factors that determine the choice of a suitable source of business finance. Several factors have been identified that affects owners financing decisions including entrepreneurial characteristics, entrepreneurs' prior experiences, business goals, business life-cycle phase, age and size of the firm, available sources of funding for growth; attitudes toward debt financing and attitudes toward personal risk. The calculation of the average cost of capital confirmed the positive impact of the drawn long-term bank loan on the total cost of capital. At the same time, it demonstrated the positive impact of realized investments on the return on equity due to the leverage effect. By applying the theory of the U-curve, a 30% share of foreign sources was proposed. At this level, the company would achieve the minimum total cost of capital and at the same time the maximum market value.