The paper analyzes assigning subject headings to works of fiction, with special emphasis on the practice of content designation and assigning subject headings to works of fantasy and science friction in the online catalogue of the Zagreb City Libraries. The results are compared to content designations from the Library of Congress online catalogue, and to the data retrieved from Wikipedia. The starting assumption of this paper is that certain types of library materials, in this case works of fantasy and science fiction, do not satisfy information needs of users and potential users (i.e. readers of the aforementioned genres) because their subject analysis is insufficient. For the purposes of this pilot study, a number of titles belonging to the two genres were selected, and their existing content designations, as assigned in the online catalogues of the Zagreb City Libraries and the Library of Congress, and in Wikipedia, were analyzed. Modern technologies have brought great changes in the way information are created and searched for, but they have also changed users’ wishes and needs, as well as searching procedures used by information and reference services. Consequently, information institutions should change and constantly adapt to the changing environment in which they operate. This also implies the need to standardize the practice of subject analysis of the works of fiction (which has traditionally been given less attention then the subject analysis of non-fiction works), while taking into account the profitability of investing additional time and effort required for subject analysis of fiction