Under the heading of Decision Theory, the literature offers an account of the ways people actually make decisions and a discussion on the mechanisms underlying this behavior. This is called a “descriptive” decision theory. On the other hand, we can also find discussions about the principles to consider making rational decisions. In this case, we have a “normative” decision theory. In this article, we are going to discuss and analyze the normative and descriptive decision theories. Also we’ll analyze the main decision models which represent these decision theories.