Provided are the data and scripts that support the findings of the study "When Attitudes and Beliefs get in the Way of Shared Decision-Making: A Mediation Analysis of Participation Preference". Introduction: Certain sociodemographic characteristics (e.g., older age) have previously been identified as barriers to patients’ participation preference in shared decision-making (SDM). We aim to demonstrate that this relationship is mediated by the perceived power imbalance that manifests itself in patients’ negative attitudes and beliefs about their role in decision-making. Methods: We recruited a large sample (N = 434) of outpatients with a range of urological diagnoses (42.2% urooncological). Before the medical consultation at a university hospital, patients completed the Patients’ Attitudes and Beliefs Scale and the Autonomy Preference Index. We evaluated attitudes as a mediator between sociodemographic factors and participation preference in a path model. Results: We replicated associations between relevant sociodemographic factors and participation preference. Importantly, attitudes and beliefs about one’s own role as a patient mediated this relationship. The mediation path model explained a substantial proportion of the variance in participation preference (27.8%). Participation preferences and attitudes did not differ for oncological and non-oncological patients. Conclusion: Patients’ attitudes and beliefs about their role determine whether they are willing to participate in medical decision-making. Thus, inviting patients to participate in SDM should encompass an assessment of their attitudes and beliefs. Negative attitudes may be accessible to change. Unlike stable sociodemographic characteristics, such values are promising targets for interventions to foster more active participation in shared decision-making. Patient or Public Contribution: This study was part of a larger project on implementing shared decision-making in urological practice. Several stakeholders were involved in the design, planning, and conduction of this study, e.g., three authors are practicing urologists, and three are psychologists with experience in patient care. In addition, the survey was piloted with patients, and their feedback was integrated into the questionnaire. The data presented in this study is based on patients’ responses.