Aim. The purpose of this action research study was to enable a group of mental health consultant nurses in the UK to map the scope and dimensions of their roles. This initial benchmarking exercise is a precursor to the development of plans for role improvement and evaluation. Background. There is a growing body of literature that addresses advanced nursing practice roles. There is, however, no international agreement on what constitutes an advanced practice role. A few countries have addressed the statutory requirements governing such roles. Consultant nurses’ roles in the UK are relatively new innovations that aim to enhance care. However, only a few investigations have evaluated the dimensions and impact of these roles. Methods. The study was framed by use of action research as a form of self-reflective enquiry. Initial data were generated through use of four focus group discussions, which were held with a group of consultant nurses employed predominately at a mental health National Health Service Trust. Five structured confirmatory questionnaires developed from the focus group data were also administered. Findings. Analysis of the focus group data gave five themes, 71 categories and 271 items that were used to inform development of the questionnaires. Responses to the questionnaire showed that 61% (n = 166) of the items had non-consensus responses. It was found there was most consensus relating to leadership theme with 63% (n = 19) items having consensus responses. Least agreement was found in the education theme where there was <15% (n = 5) agreement to individual items. Conclusions. The study demonstrated complexity and variety in how the consultant nurses’ roles in the UK are being developed. Relevance to clinical practice. The potential for consultant nurse roles to enhance patient care is tremendous. This study provides initial indicators, which the practitioners involved, can use to plot future developments and changes to their roles.