INTRODUCTION: We conducted a systematic review of primary evidence to clarify what information influences treatment selection by patients with early stage prostate cancer. MATERIALS AND METHODS: We conducted a systematic review of the Web of Knowledge, using the all databases option. Papers were then triaged out on the basis of the title and/or abstract, leaving 120 papers. Reviewing the full papers resulted in a final corpus of 21 papers. RESULTS: The data suggest that patients typically balance potential benefits against potential side effects but in a complex way with large variation across patients. For some patients, potential benefits relate to chances of survival but, for others, relate to control over cancer spread. The most common potential harm is effect on bladder functioning but even that is not a concern of all patients. Similarly, potential impact on bowel and on sexual functioning affects some patients decisions but not others. Patient decisions are also affected by information not typically identified as affecting this decision. These include aspects of treatment and decision processes, competencies, and others opinions, again, with wide variation across patients. The patients view of which information items affect his decision may also change over time, consistent with a dynamic decision-making process. CONCLUSIONS: Decision support interventions are needed to optimally tailor information for decision-making to the individual patient, and should be designed to accommodate the illustrated variation in patients needs.