The aim of this paper is to determine the market structures and their characteristics. The market structure shows the circumstances and the conditions under which some good will be sold and bought in the market. Depending on the different criteria, there may be more or less market conditions. P.A. Samuelson distinguishes three basic market structures: perfect competition, imperfect competition and perfect monopoly, based on three basic criteria (number of participants, product differentiation, impact on price) and two secondary indicators (sales and marketing methods and part of the dominant economy). S. Weintraub defines four different market structures based on three criteria (number of participants, coefficient of substitution elasticity and cross-demand elasticity coefficient). This classification is most commonly used in price and output determinations, and the basic features of particular market structures are the following: perfect competition, monopoly, oligopoly and monopolistic competition. In general, perfect and imperfect competition can be distinguished. There are large number of participants in perfect competition, and sellers cannot influence the price of their product, while in imperfect competition some sellers may affect the price of their product. The market structures of imperfect competition are: monopoly, oligopoly and monopolistic competition.