Trust in institutions of political and social system is basis of modern democracies. The article is based on research of trust in state and civil society institutions, that was carried out within the program Slovenian public opinion in the period from 1991-2006. Higher level of trust in state and lower civil society institutions in start (1991) followed by a decline and stagnation of trust in political institution on a low level in the first decade (1991-1999) - and at the same time rise of trust in civil society institutions, all characterize the course of democratic institutionalization in Slovenia in this period. Short-term change of rulers and elections in 2000 are characterized by increase of level of trust in institutions to the upper limit, followed by another decrease in political institutions - in spite of changes in power positions in 2004 - on the lower level in comparison to 1999. The analysis confirms that expression of trust in political institutions is under the strong influence of political views of the evaluators. The Slovenian results are compared to international ones. The author calls attention to Slovenians' low level of trust in political institutions in the recent period, which limits participation of Slovenians in the democratic processes and successfulness of their control over legislative and executive power. Processes of political decision-making thus lose wide democratic basis and remain in the hands of "power owners".