Terms, such as market, competition and market forms of imperfect competition, are defined by this final work. A market is a place where sellers who offer their products and buyers of these products meet, while prices represent the amounts at which market participants exchange goods and services. There are differentiated and homogeneous products on the market. Differentiated products are those that differ in certain specified and particular features, while homogeneous products have substitutes and their selection is dictated by price. Depending on the market structure, bidders have a greater or lesser influence on prices. Competitiveness is manifested in the success of a company when competing with its rivals. Forms of imperfect competition are monopoly, duopoly, oligopoly and monopolistic competition. In this final work, the concept of economies of scale is also elaborated, appearing as a form of imperfect competition with homogeneous products. The purpose of the paper was to explain the main market conditions and make them clearly apparent using examples from the Croatian economy. Additionally, antitrust legislation has been addressed. In this work, the main determinants of each market situation can be deduced, while at same time both positive and negative sides of monopoly, state-owned, and private companies are shown.