The issue of capital structure is still a highly debated and unresolved topic in corporate finance. Most studies on this topic are addressed by companies in the United States, the United Kingdom, and other countries of predominantly Western Europe. This article deals with Czech enterprises, as they are not so often the subject of research. The paper aims to determine the influence of three determinants on the leverage ratio of energy companies during the period from 2009 to 2017. Energy companies were selected for their influence on all other industries. Moreover, the energy sector itself is affected by some factors - raw material prices, energy policy and legislation in Europe and the world. There is a survey of the relationships between the share of fixed assets, return on assets, and macroeconomic development, which is represented by GDP growth rate, on total, long-term and short-term debt of the companies. A negative relationship is expected for economic growth and more profitable firms, a positive relationship for the structure of assets. The research of the companies is performed by correlation analysis and Generalized Method of Moment in econometric software EViews. The findings of both analyses indicate a positive relationship between asset structure and almost all forms of debt. A strong relationship is observed mainly for total and short-term debt. GDP growth has a significant negative influence on total and short-term debt. Found impacts live up to expectations. Unfortunately, the impact of profitability was not proven in one case.