The development of the service sector is an outstanding feature of the world economy. In the non-favorable economic environment and increasing competition the main goal of Russian companies in the sphere of services is to increase their competitiveness. The solution of this problem requires the formation of a methodical approach to assessing and analyzing the real state of the competitiveness of enterprises. The article describes main features of the IT-service sector (the most promising and dynamically developing sectors of the Russian economy) and main problems of IT companies’ activity. Practical methods for assessing the competitiveness of service enterprises are analyzed, and the disadvantages of these methods are revealed. A methodical approach to assess the competitiveness of IT companies is proposed, which takes into account the features of companies’ functioning and includes an objective and labor-saving procedure of evaluation. At the first stage of the study factors determining the competitiveness of an IT company are defined: current efficiency and adaptability. The main characteristics of the factors are considered and their impact on competitiveness is analyzed. The key role of an adaptive component, used in evaluation of the competitiveness of IT companies in a rapidly changing external environment is proved. The adaptability of the enterprise is analyzed using the example of the 20 most successful Russian IT companies in terms of market share dynamics, and a graphic interpretation of the assessment is provided by building a competitive field. The position of each company in the competitive field is revealed, a map of strategic groups is drawn up for quantifying the competitive position of competing enterprises. Analyzed enterprises are divided into the following groups: leaders, unstable leaders, persecutors and laggards. Based on the results of the competitiveness assessment, it was suggested to develop measures for further developing or changing the competitive position of a particular company in accordance with identified challenges.