The objective of this study is to analyse how changes in relevance criteria are related to changes in problem stages during the task performance process. Relevance is understood as a task‐ and process‐oriented user construct. The assessment of relevance is based on both retrieved bibliographical information and the documents acquired and read on the basis of this information. The participants of the study were eleven students who attended a course for one term for preparing a research proposal for the master’s thesis. The students were asked to make an IR search at the beginning, middle and end of the course. Data for describing their understanding of the work task, search goals and tactics as well as relevance assessments were collected during the search sessions. Pre‐ and post‐search interviews were conducted during each session. The students were asked to think aloud during the search session. The transaction logs were captured and the thinking aloud was recorded. Research and search diaries were also collected. The findings support to a certain extent the overall hypotheses that a person’s problem stage during task performance is related to his or her use of relevance criteria in assessing retrieved references and documents. There is a connection between an individual’s changing understanding of his or her task and how the relevance of references and full texts is judged. The more structured the task in the process, the more able the person is to distinguish between relevant and other sources. The relevance criteria of documents changed more than the criteria of references during the process. Moreover, it seems that understanding of topicality varies depending on the phase of the process.