The article considers the results of studying the Online Public Access Catalogue (OPAC) functionality, revealed by specialists of domestic and foreign libraries. The user survey results showed that OPAC of foreign libraries provides a more developed search system than the OPAC of domestic libraries. While a foreign user is able to interact with a catalogue in a natural language, domestic library OPAC operate mostly in a query-response mode. The problems were revealed which the user encounters during information search, connected with information perception, granting incomplete information on library collections, and absence of stability in work of servers. Often, there is no tooltip system. Users cannot understand the content of classification indices. It is difficult to find information about the library and access to OPAC on university websites, as this information is not always easily accessible. On the other hand, there is often a low level of user information culture. Most of them do not have the skills to write search queries and use logical operators. Maintaining OPAC in different automated library and information systems (ALIS), involving different options for combining, shortening, clarification of terms in information search, exacerbates these problems. After all, even advanced users may get incomplete search results assuming that library ALIS works similarly to other systems they are familiar with. It negatively affects the OPAC use efficiency. Ways of solving the revealed problems are suggested. Conducting regular training activities for OPAC users, development and improvement of tooltip system, ensuring integrated search in all library databases, providing information on classification information retrieval languages, conducting retrospective conversion of card catalogues, ensuring completeness and accuracy of provided bibliographic data, conducting systematic research to identify user requirements for the functionality of the electronic part of the reference and search apparatus will facilitate the process of searching and obtaining data about library information resources, improve the quality of OPAC information.