The topic of the paper is an analysis of the term opposition (its definition and role) as an important factor within functioning of non-democratic regimes. The paper tries to conceptualize the term opposition in non-democratic regime, to compare it with general definition of that term (formulated for the consolidated democracy as the research framework) and to evaluate existing selected theories handled with an opposition in non-democratic regimes. The aim of the paper is to identify problematic aspects, or to evaluate possibilities and limits for analysis of function of non-democratic regimes, which are offered by the term opposition and related theories.