Discovery systems allow academic library users to locate a wider range of resources than previous OPACs. However, actual usage of these systems may still be challenging. The main aim of this research is to get a better understanding of the hurdles users face while searching contemporary library systems.This study utilizes a transaction log analysis approach, using popular and zero result queries datasets gathered from the statistics module of a library discovery system. It explores what types of queries users perform, how successful the queries are, and examines underlying reasons for unsuccessful queries. To our knowledge, this is the first academic paper to use data originating from built-in transaction logs of the Oria library discovery system.The analysis shows that queries are often curriculum-related: we could pinpoint a relation with curriculum for 58% of the popular queries, and 28% for the zero result searches. A vast majority of popular queries refer to books, databases and journals, and over half of the queries used the title to locate a resource. 20% of the popular queries turned out to be unsuccessful. Zero result queries typically involve long queries, and in many cases consist of pasted reference citations.Our conclusion is that the examined discovery system is rather sensitive. Whilst this suggests the importance of increasing users' information search skills, it also points to the need for enhancing discovery systems and their underlying metadata. Furthermore, due to the prominence of curriculum-related queries, a better integration of curriculum materials ought to be achieved.