Subject. The article considers the capitalization of oil and gas companies. Objectives. The purpose is to research and evaluate the capitalization of the said companies. Methods. The study rests on general scientific methods of analysis. Results. The paper formulates the concept of capitalization as the most important result of the economic efficiency of production, investment attractiveness, and prospects for the development of corporation's business. It shows that the efficiency of using available resources is a crucial factor for capitalization. It considers the opportunities to single out fictitious value in market capitalization, using the fair value calculation method. This enables investors to make more informed investment decisions. The paper also identifies problems related to capitalization growth in the oil and gas business, and gives recommendations for its improvement. Conclusions. Capitalization growth should be seen as the main goal of sustainable development of companies. The concept of market capitalization should be tied to the assessment of economic performance. At the present stage, the paper reveals that the market capitalization index is away from actual business results, with the accumulation of fictitious capital in value.