BACKGROUND: Advance care planning discussions exploring future care and support needs can be beneficial to people with advanced illness. While research has focussed on barriers, outcomes, and completion, little is known about how discussions influence thoughts, feelings, and behaviours. AIM: To explore experiences of advance care planning for people with incurable life-limiting illnesses, to understand the impact of discussions on individuals, and factors influencing psychological responses. DESIGN: Semi-structured qualitative interviews were conducted. Data were analysed using framework analysis. Reflexive journalling and discussion of coding framework and themes supported rigour. SETTING/PARTICIPANTS: Twenty purposively sampled adults receiving hospice care, aged 30-93 with cancer ( RESULTS: Advance care planning elicits multiple complex thoughts, emotions, and behaviours, with responses ranging from the procedural to the profound. Discussions empowered and instilled confidence, promoted openness with relatives, encouraged people to make the most of their time remaining, and sometimes contributed to coming to terms with their mortality. Factors influencing experiences of discussions reflected the complexity and diversity in participants' lives, personalities, and life experiences, with discussions exposing the realities of living with terminal illness. CONCLUSION: Individuals' unique lives and experiences shape their responses to, and the impact of advance care planning on how they think, feel and behave. Advance care planning is not simply a means to document end-of-life care preferences, but can empower and instil confidence in patients, and may form part of the process of coming to terms with mortality, allowing clinicians to shift focus from process-related outcomes.