Aims : Decision aids in practice may affect patient trust in the clinician, a requirement for optimal diabetes care. We sought to determine the impact of a decision aid to help patients with diabetes decide about statins (Statin Choice) on patients' trust in the clinician. Methods : We randomized 16 diabetologists and 98 patients with type 2 diabetes referred to a subspecialty diabetes clinic to use the Statin Choice decision aid or a patient pamphlet about dyslipidaemia, and then to receive these materials from either the clinician during the visit or a researcher prior to the visit. Providers and patients were blinded to the study hypothesis. Immediately after the clinical encounter, patients completed a survey including questions on trust (range 0 to total trust = 100), knowledge, and decisional conflict. Researchers reviewed videotaped encounters and assessed patient participation (using the OPTION scale) and visit length. Results : Overall mean trust score was 91 (median 97.2, IQR 86, 100). After adjustment for patient characteristics, results suggested greater total trust (trust = 100) with the decision aid [odds ratio (OR) 1.77, 95% CI 0.94, 3.35]. Total trust was associated with knowledge (for each additional knowledge point, OR 1.3, 95% CI 1.1, 1.6), patient participation (for each additional point in the OPTION scale, OR 1.1, 95% CI 1.1, 1.2), and decisional conflict (for every 5-point decrease in conflict, OR 1.5, 95% CI 1.2, 1.9). Total trust was not associated with visit length, which the decision aid did not significantly affect. There was no significant effect interaction across the trial factors. Conclusions : Preliminary evidence suggests that decision aids do not have a large negative impact on trust in the physician and may increase trust through improvements in the decision-making process. © 2009 Blackwell Publishing Ltd.