Purpose. The purpose of this paper is to emphasize the diffi culties in the process of creatig the library development guidelines document, its importance and the elements it should include, and then present all these factors on the example of creating the collection development guidelines in the University Library Rijeka. Approach/Methodology/Design. The paper presents several defi nitions of collection development guidelines, emphasizes their signifacance and the necessity of creating this document for libraries, as well as the elements it should contain. The paper presents the results of the research conducted by browsing the web sites of six Croatian university libraries in December 2016, and then discusses the fundamental principles of collection development guidelines in the University Library Rijeka. Findings. In the process of creating the guidelines for the University Library Rijeka, the selected theoretical fi ndings as well as some examples of good practices in Western European and American university libraries were used. Practical implications. The presented data and the examples may serve as a model to other libraries that decide to create and implement their own library collection development guidelines. Originality/Value. The research results have shown that the practice of creating the collection development guidelines is still not widely accepted in Croatian libraries. The authors point out the importance of creating this document and making it public for libraries, emphasizing that it should be one of the fundamental documents in library business.