Problem: Truth-telling is an important component of respect for patients' self-determination, but in the context of breaking bad news, it is also a distressing and difficult task. Intervention: We investigated the long-term influence of a simulated patient-based teaching intervention, integrating learning objectives in communication skills and ethics into students' attitudes and concerns regarding truth-telling. We followed two cohorts of medical students from the preclinical third year to their clinical rotations (fifth year). Open-ended responses were analysed to explore medical students' reported difficulties in breaking bad news. Context: This intervention was implemented during the last preclinical year of a problem-based medical curriculum, in collaboration between the doctor–patient communication and ethics programs. Outcome: Over time, concerns such as empathy and truthfulness shifted from a personal to a relational focus. Whereas ‘truthfulness' was a concern for the content of the message, ‘truth-telling' included concerns on how information was communicated and how realistically it was received. Truth-telling required empathy, adaptation to the patient, and appropriate management of emotions, both for the patient's welfare and for a realistic understanding of the situation. Lessons learned: Our study confirms that an intervention confronting students with a realistic situation succeeds in making them more aware of the real issues of truth-telling. Medical students deepened their reflection over time, acquiring a deeper understanding of the relational dimension of values such as truth-telling, and honing their view of empathy.