Political systems need constant, permanent confirmation of its’ legality; the most important way to ensure continuity of this process in contemporary democracies is citizens political participation. Taking part in political life may evince in many ways and serves both in order to expressing support (which increases system legitimacy) and to raise an objections, demonstrate disapproval or even to revolt against the system as a whole or its’ part (which decreases or even abolish system legitimacy). This paper contains considerations over dependencies among political participation and political system legitimization focusing on emerging democracies in transformation. Analysis concerns such forms of political participation as: interest in politics, voting, engaging in social and political group activities, belonging to social and political organizations and taking part in politics by violent behavior. Attention was also given to empirical data from Polish General Social Survey and European Social Survey and concentrated on the process of legitimization of Polish political system by various forms of citizens political participation. Paper also introduces typology of attitudes to political system and its influence on political system legitimization. Attitudes of support, indifference, alienation and resistance were distinguished. Also the fifth type of attitudes was identified that seems to be the most important, useful and desired in consolidating democracies that was called – critical support.