The classical theories of social capital identify its two dimensions: structural capital and cognitive capital. The structural dimension is associated with networks and connections within groups, while the cognitive dimension concerns trust and social norms that affect the building of communication and community. The paper discusses the concept of "trust", which is believed to be a necessary condition to develop social capital and crucial in building relationships among library employees as well as contacts with the external environment, in particular the local communities visiting the library. Trust strengthens relationships with the neighbourhood, facilitates cooperation with partners and colleagues, reduces fear and conflicts, and may also stimulate development. Accordingly, this factor should be taken into consideration by library managers in their managerial decisions. In order to analyse trust among library workers, a study was conducted in 20 countries of the world. The analysis presented in the paper determined both the level of trust among the professional group of librarians and its correlation with other factors (independent variables, such as age, type of library, position, etc.) and dependent variables. It was established that librarians have a high level of trust in other people and that respondents declaring to trust others also have a higher level of individual social capital and a larger social network, are more willing to engage in charity and civic activities, and family and friends are important to them. It seems that such pro-social attitudes may be particularly desirable on specific positions within the library structure: those involving direct contact with patrons and managerial positions.
