BACKGROUND Advance care planning (ACP) is a process of discussing and recording patients' preferences for future care, aiming to guide healthcare decisions at the end of life (EOL). AIM To explore nuances in the long-term impact of ACP by studying patient and relative experiences. DESIGN A qualitative follow-up interview study. Interviews were recorded, transcribed and analysed using thematic synthesis. SETTING/PARTICIPANTS 3 patients with a life-limiting disease (lung or heart disease), affiliated with a major Danish hospital, and 7 relatives were interviewed 1 year after participating in an ACP discussion. RESULTS The experiences were diverse. Some patients and relatives felt 'relieved', 'more secure' and more in control due to ACP. To some, ACP had led to open communication rather than 'beating around the bush', and to spending more quality time together. However, others perceived ACP as irrelevant. Some stated that the patient's wishes had not been met regardless of ACP. Others felt that EOL questions cannot be realistically considered until 'you're in the middle of it', because many factors are involved. In one case, participating in ACP led to a patient-relative conflict, resulting in EOL issues being 'tucked away'. CONCLUSIONS The study reveals great diversity in patient and relative experiences of ACP. The study challenges previous research which mainly emphasises ACP as a valuable tool to optimise EOL care. This study stresses the importance of awareness of the highly individual nature of preferences and needs of patients and relatives regarding information, involvement and communication about EOL care.