The focus of this article is to analyse the impact of capital structure on the value of energy sector companies listed on the Warsaw Stock Exchange. The proposed study will cover the last four years, i.e. 2014-2017, in quarterly terms. In addition to the mentioned capital structure parameter, the analysis also covers such indicators as return on equity (ROE) and return on assets (ROA). The study will use multiple regression based on the deltas of the respective parameters describing their changes quarter-to-quarter. The author of this publication assumes that capital structure may have an impact on the value of energy sector companies. The assumption is based on the market phenomenon whereby capital structure seems to reflect to a certain extent the risk incurred by investors: on the one hand, the higher the share of borrowed capital in financing an enterprise’s operations, the higher the risk; on the other hand, the higher the proportion of equity in the financing of corporate operations, the lower the chance for dividends to be paid to investors in the respective companies. Investigating the mentioned phenomenon will make it possible, to a certain extent, to answer the question of whether Polish investors are more willing to accept investment risk in exchange for a higher return on investment or whether they would rather limit investment risk and yield lower profit from the capital invested in a given enterprise.