The classical models of the Modern Finance Theory are based on the rationality, where the investor uses the utility curve to maximize his wealth. However, many studies show that the decision process does not always occur in a rational manner, leading the investor, many times, to wrong decisions. The Behavior Finance appears to question the assumption of the unlimited rationality. It incorporates the psychology and the sociology to the classical models with the purpose of better understanding the decision process in the financial environmental. This work intends to analyze certain behavior aspects and compare the susceptibility of two groups of investors to such aspects: the institutional investors and the individual investors. To compare and test such susceptibility, questionnaires have been sent to such two groups of investors. The answers were analyzed through statistics tests. Such tests indicated that the individual investors are more susceptible to behavior tendencies then institutional investors.