Compared to the scholarship on general political trust, relatively little attention has been paid to institutional trust. Research on the subject tends to treat political institutions as single entities, ignoring the fact that different institutions can enjoy, in the long term, very different levels of trust. This paper builds on the assumption that institutional trust may be formed differently depending on the institution type, and thus aims to explain how trust is formed in different types of democratic institutions. Moreover, it explains how the relationship between trust in a political institution and voter turnout can change depending on how trust is formed. The study is based on the content analysis of 30 semi-structured interviews from the Czech Republic. The study shows that respondents tend to develop trust in a political institution based on their assessment of the institution’s current performance and outcomes rather than their assessment of the institution itself. The study argues that an integral part of the concept of trust in a political institution is the popularity of the politicians who represent the institution. However, how trust is formed depends on the type of institution, which has important implications for measuring this concept. The relationship between institutional trust and turnout may also vary depending on how trust in an institution is formed. Thus, a potential correlation between trust in an institution and electoral participation may exist depending on the type of an institution.