Cultural activity undertaken by public cultural institutions is very complex. This causes several problems in assessing effectiveness of such organizations. The aim of this paper is to indicate a theoretical framework of effectiveness, adjusted to the specificity of this sector. The article presents a brief review of basic theoretical frameworks of effectiveness, including their critic. The concept indicated as most appropriate for cultural institutions is effectiveness based on agathos concept. In order to include the specificity of culture sector it was supplemented by defining crucial dimensions of mission in cultural institutions. One of the most important conclusions is, that indicated theoretical framework of effectiveness may be used also for public and nonprofit organizations.