Introduction: The Internet has radically changed the global availability of scholarly publications. Today, a substantial part of the resources accessible for researchers and university students are offered through electronic site licenses, making the supply of easily obtainable information larger than ever. This brings forth an important question: what are the qualitative and quantitative effects of this development on the use of reference material in research and studies? Method: To address the research question, reference lists of Masters' theses from 1985, 1993 and 2003 were studied in three disciplines: economics, psychology and mathematics, followed by semi-structured interviews of students who had finished their thesis in 2003. Analysis: The quantitative data were analysed using analysis of variance (ANOVA) with the statistical program SPSS, where the significance of the results was measured with Dunnet's t-test. Results: The findings showed a substantial increase in the use of scholarly articles as references throughout the studied time periods, although the amount of other information sources had remained largely unchanged. There were also significant differences between the three disciplines in the contents of their reference lists, the amount of Internet resources that students used, how they sought and obtained publications, and how they selected their sources. Conclusions: The Internet appears to have had a profound effect on the type and quantity of information that students use as references in Master's theses. One of the main problems that students reported was a lack of training in information seeking, and the abundance of irrelevant information on the Internet. Many respondents would have needed additional training on using library databases.