This thesis has been motivated by past research, problems and realizations that online library catalog users frequently perform subject searches – using keywords, subject headings and descriptors – and these searches have yielded unsatisfactory results. Web-based catalogs or WebPACs (Web-based Online Public Access Catalogs), belonging to the so-called third generation of online catalogs and providing a wide variety of search options, remain largely underutilized despite the continuous advancement of information retrieval systems. Users still encounter a number of problems, such as those related to translating their concepts to the language of the catalog’s system and cross-references prepared to this purpose. Subject access in online library catalogs can be provided through different access points. To that purpose natural and controlled indexing and retrieval languages are used, and each among them has its advantages and downsides. Natural language indexing is performed by the computer, in which process words from defined fields are automatically extracted. Controlled indexing languages are those in which selection of terms to be assigned to documents is manually performed. These are, for example, classification systems, subject heading languages and thesauri. During the 1970s, a consensus was reached that the best retrieval results are gained when using both types of indexing languages simultaneously. Apart from indexing languages, it is necessary to take into account user search behavior; and while designing user interface one has to allow for the users’ skills and knowledge - ensuring instruction, help and feedback information at every step of the retrieval process. The aim of the research was to determine the variety and quality of subject access to information in WebPACs of British university libraries, including searching by words or classification marks, natural and controlled languages, browsing options, and forming simple and complex queries in order to conclude about existing advancements, offered models and employed methods and compare them to WebPACs of Croatian university libraries.