EN
This paper presents the issue of significance of knowledge and self-knowledge in the decision making processes of adults and adolescents. Knowledge is the foundation of every decision a person takes. It may be called the 'building material' which decisions are made from (Bross 1965). Knowledge has a regulatory role in decision making processes, influencing a persons actions. This study presented the following issues: 1) Knowledge as a reproductive and generative system (Tomaszewski 1976), 2) The significance of knowledge in decision making processes, mostly in theory discourse concerning the role of information in decision making processes (Bross 1965, Kozielecki 1975, 1992, Tyszka 1986), 3) Analysis of sample research on the significance of knowledge and self-knowledge of a person in decision making processes (Kozielecki 1975, Tyszka 1986, Walesa 1977, Biela 1976, Goszczynska 1977, 1997, Czerwinska-Jasiewicz 1977, 1997). On the basis of the theory presented as well as a detailed analysis of the test results, one can confirm the significance of knowledge and self-knowledge in the process of decision making by a person. Both knowledge of the world and self-knowledge has a regulatory function in this process, influencing a person's actions (their functioning and concrete actions).