Quantitative research has shown Mindfulness-based Stress Reduction (MBSR) programmes can reduce mood disturbance, improve quality of life, and decrease stress symptoms of cancer patients. However, the range of subjective effects experienced by programme participants has not been clearly described. Nine cancer patients who had participated in an 8-week MBSR programme through the Tom Baker Cancer Centre's Department of Psychosocial Resources, and who continued to attend weekly drop-in MBSR sessions were interviewed for this study. Qualitative research was conducted using grounded theory analysis. Data from semi-structured interviews and a focus group were analysed using QSR N6 software to identify themes concerning the effects patients experienced by adding meditation to their lives. Five major themes emerged from the data: (1) opening to change; (2) self-control; (3) shared experience; (4) personal growth; (5) spirituality. This information was used to develop specific theory concerning mechanisms whereby MBSR effects change for cancer patients. These understandings may be used to refine and further develop MBSR programmes to better assist patients during cancer diagnosis, treatment and recovery. Copyright © 2006 John Wiley & Sons, Ltd.