The study aims to elicit user requirements for internet-based applications disclosing fellow patients' illness stories for the benefit of breast cancer patients. Twenty-six breast cancer patients, recruited via the Dutch Patient Organization for Breast Cancer, were interviewed about their preferences with regards to content, appearance, and search options concerning fellow patients' illness stories online. The interviews were analysed quantitatively (SPSS) and qualitatively (NVivo). Participants were mainly interested in fellow patients' experiences about how to cope with emotions, the impact of cancer in daily life, and physical discomforts. Most participants preferred a section of an illness story in text format about a specific topic; some of them wanted to be able to click on to the corresponding complete story, comprising of text alone or supported by voice or video clip. A majority of participants wanted to be able to select illness stories on the basis of several authors' features, i.e. treatment underwent, age, presence of metastases, time since diagnosis, and whether or not caring for children. Participants gave arguments for their preferences. The findings of this study will be used for designing an online trial with breast cancer patients aiming at refining the user requirements. Copyright © 2007 John Wiley & Sons, Ltd.