This thesis contributes to the discussion on the use of library plans in public libraries in Sweden. Library plans were made mandatory 15 years ago, and the thesis’ aim is to further our knowledge about whether or not library plans of public libraries in Sweden are being used as an instrument of effectiveness or as something else. The study was carried out by applying qualitative document analysis to ten up-to-date public libraries’ library plans and by reviewing them through the lens of organizational theory. The goals in each library plan were compared to the public activities offered at the library in order to examine to what extent the public activities could be means to achieve the goals in the corresponding library plan. The results show that the ten library plans hardly functioned as an instrument of effectiveness. According to organizational theory, the goals could be considered to be of an official, symbolic, visionary and complex character, which made the analysis of the public activities as means to achieve the goals difficult to carry out. Goals of an operational, realistic or simple character, which according to the theoretical framework would imply the use of the plan as an instrument of effectiveness, were rare. Rather, the libraries seemed to use the plans for communicating their purpose and their importance to their external environment, which in turn implies that the plans were being used for attaining legitimacy.