While in the theory of rational decision making, it is considered that people's choices remain consistent and predictable even in cases when same information is presented in different ways, in real situations consumers' decisions are affected by their personal characteristics, habits, norms and past experience, as well as limitations of human cognitive mechanisms. In general, heuristics can be perceived as fast cognitive processes in decision making which can sometimes lead to the occurrence of biases which shape the final decision. In marketing communication, the general capacity of people to make cognitive errors encourage the application of certain principles in formulation of messages in order to instigate recipients to make predictable cognitive errors when making decisions. The subject of the research is to determine how the encouragement of cognitive biase sin marketing communication can affect decisions of messages recipients. The research included the application of two research methods observation and experimental method. In as many as 80% of the observed advertisements, the encouragement of at least one cognitive bias was registered. In both experimental situations, it was shown that the willingness to pay for a product depends on the way the promotional message is formulated.