This qualitative study aimed to explore an under-researched issue within the emerging body of research about carers and personalisation - the carer-service user relationship. It was carried out across 11 English local authorities between 2011 and 2012 and focused on the impact of a change in the service user's social care arrangements to a personal budget on this relationship. Using purposive sampling and explicit inclusion criteria, data were gathered through semi-structured in-depth interviews with 23 carers in long-term dyadic relationships with an adult in receipt of social care who had changed to a personal budget. The interviews explored carers' perceptions of the carer-service user relationship before and after the advent of the personal budget and changes that had occurred. The findings were thematically analysed and reflect the fact that in addition to the effects of the move to a personal budget on the carer-service user relationship, the interviewees talked at length about a range of other effects of this move. Just over half of those interviewed felt that the personal budget had enhanced the carer-service user relationship. The other effects were both positive and negative. Three quarters reported positive outcomes, such as feeling happier, healthier and having more control over their lives. Although two thirds experienced negative feelings about having less involvement in the service user's care, these feelings eased over time and if they had confidence in the quality of the care. Over half found administering the personal budget stressful. Further analysis of these findings showed the study contributes not only to existing knowledge about the carer-service user relationship within personalisation but also to knowledge about the effects of personalisation on carers more generally. It therefore simultaneously develops the emergent knowledge base about carers and personalisation. Recommendations based on this analysis are made about future practice and research.