Quality of care is often described by professionals. However, in this study breast cancer patients participated in developing an instrument that reflects quality of care from the patient's perspective. Through focus groups and concept mapping patients' ideas on determinants of good quality of care were generated and categorised according to similarity and importance. Information from eight focus group interviews with a total of 72 participants yielded 221 quality of care aspects. Following reduction, 81 aspects were used for categorisation during six concept mapping sessions with 67 participants. After analysis, 55 aspects remained grouped into six clusters. This study was conducted with a large number of breast cancer patients, undergoing the full range of treatment modalities, in different hospitals, in different areas in the Netherlands. Therefore, this set of quality of care indicators can be considered valid and suitable for the evaluation of breast cancer care as experienced by patients.