Purpose: Recent studies have found significant variability in patient preferences for participation in medical decision-making with more than half of respondents preferring to leave the final decision up to their doctor. Underestimation of patients' preference to participate in decision-making may be in part due to the lack of concept validity in the domains used to quantify patients' preferences. If this hypothesis is correct, current surveys may fail to query subjects on domains which patients feel characterize active participation. The purpose of this study was to better understand how patients conceptualize the process of active participation in decisions related to their health care. Methods: A qualitative study was chosen as the best approach to allow the patients to frame the decision-making process from their own perspective and to avoid imposing any assumptions about how this process is defined. Individual face-to-face audiotaped interviews were conducted until thematic saturation was reached. The constant comparative method approach to analysis was employed to ensure that the analysts defined the codes in a consistent manner across all transcripts. Results: Twenty-six persons were interviewed: 96% women; all Caucasian; 69% married; 50% college graduates; and 23% retired. The main themes which arose during the interviews are distinct from those included in most previous studies quantifying patients' preferred role in decision-making and include: 1) decision-making is often a continuous process in which preference for participation may change over time, 2) decision-making is not performed in isolation, but often involves a larger social context, 3) choices do not usually center around which treatment option or screening strategy to pursue, but when to change doctors and whether or not to accept a physician's recommendation, 4) decision-making almost always occurs in the context of a physician's recommendation, and 5) choices are made in the context of each patient's “health-belief” model. Conclusions: Subjects in this study viewed active participation as including domains distinct from those traditionally evaluated in studies quantifying patients' preferred role in medical decision-making. These findings suggest that underestimation of patients' desire to participate in medical decision-making may be due, in part, to inadequate understanding of how patients conceptualize participation and consequent limitations in survey design.