The concept of market, free market, the development of competition as well as the inception of monopoly and oligopoly in the midst of a market being opened all lead towards contemplation of the role that forming of the prices has on the market, the ways in which it is legally regulates as well as the consequences price manipulation can have. There are prices which are determined not by way of supply and demand, but by the will of the manufacturer and giver of services and are still completely legal and acceptable, such as discriminatory prices. The most common form of discriminatory prices is a positive discrimination, such as cheaper move tickets for people who are retired. On the other hand, dumping prices and predatory prices can be lethal to an economy and for that reason must be stopped by way of employing measures of control as well as measures of detection of such practices. The legal framework, as well as the economical framework is extremely important in preventing such practices. In this final thesis, under the title “The role of prices on the market in Republic of Croatia”, author analyzes the terms market, price formation and price manipulation and conducts research of the use of predatory prices on the examples of HT and France Telecom.