The article discusses some ways of the monopoly power estimation by means of the mathematical indicators of market concentration. The concentration level affects the firms’ competitive behavior in the market: the higher the concentration, the more the firms depend on each other, and consequently, the more likely they will cooperate. Therefore, a high level of concentration can lead to the decrease of competition in the market. There are many different indicators of the monopolization degree of the market in economic theory. Some of the most frequently used indices of market power concentration are reviewed in the article. The consistency of these indicators to the basic antitrust regulations is investigated. The authors show that in order to obtain the reliable results each of the available methods of monopoly power detection requires the detailed market analysis.