The author probes the factors that influence the structure of service markets and describes the way in which they influence the operations of these markets. The paper presents selected factors of key importance to the structure of service markets. These include the nonmaterial nature and diversification of services, information asymmetry, natural and regulatory barriers to entry and the level of concentration. The last part of the article shows the influence of all these factors on the structure of selected service markets. The author argues that service markets have certain specific features that account for the existence of individual market models. Whether a specific segment of the service sector takes the form of an oligopoly, monopoly or perfect competition is determined by its specific features, including the differentiation of services, the nature of entry barriers, the existence of scale benefits and the level of concentration.