Objective: To develop a Consumer Quality Index (CQ-index) Breast Care instrument that measures quality of care from the perspective of patients with (suspicion of) breast cancer. Methods: To develop a pilot questionnaire, three focus group discussions with breast cancer patients were performed. The questionnaire was sent to 1197 patients. We performed psychometric and descriptive analyses to optimise the new instrument. Results: Focus group discussions revealed nine main themes related to breast care quality. Psychometric analyses resulted in 15 reliable scales. The final instrument consisted of 152 items, of which 118 items regarded patients' experiences. The aspect with the highest need for quality improvement was informing patients about a second opinion. Conclusion: The CQ-index Breast Care (CQI-BC) instrument provides a good starting point for further research on the quality of breast care seen from the perspective of patients. The newly developed instrument can be used by different stakeholders for future quality monitoring. © 2008 Elsevier Ltd. All rights reserved.