Social trust (understood as a belief that most unknown people are fair, helpful and trustworthy) is an important correlate or a part of social capital which, in turn, contributes to social and economical development of societies. In the present work indices of social trust in 24 EU countries gathered in the European Social Survey in 2004/2005 were studied. The analyses indicated that the seven countries which had experienced communism showed much lower level of trust than the 17 countries without this experience. Two explanations of the relation between experience of communism and lowered trust were proposed and tested. The first was a cultural one in terms of diminished individualism and the second was an economical one in terms of lowered economical prosperity of societies which had suffered from communism. Although post-communist countries showed both lowered GDP and the individualism level, mediation analyses showed that only the lowered level of economical prosperity accounted for the lowered trust in those countries.