Objectives To investigate the attitudes of breast cancer patients who accepted or declined participation in a randomized trial with hormone replacement therapy that might increase their risk of recurrence (the Stockholm trial). Methods A total of 115 patients free from breast cancer recurrence were interviewed; 57 were participants and 58 were non-participants in the Stockholm trial. Patients answered five questionnaires regarding information needs (two), attitudes to participation in trials (two) and patient role in treatment decisions (one). Results Participants in the Stockholm trial had a lower risk of breast cancer recurrence (measured by node-positive disease and tumor size) and were older than non-participants. Their information needs were the same. Participants in the trial were more prepared to accept uncertainty, to have an altruistic attitude, to accept risks including an increased risk of recurrence of breast cancer, if their quality of life or general health was improved. Most patients preferred a collaborative role in relation to their physician but participants often wanted more influence than they had in treatment decisions. Conclusion A patient's decision to accept or decline participation in the Stockholm trial was influenced by her objective risk of breast cancer recurrence and reflected her attitude to risk, uncertainty and preference to be active in treatment decisions.