BACKGROUND AND OBJECTIVES: The EORTC Quality of Life Utility Core 10 Dimensions (QLU-C10D) and the Patient-Reported Outcome Measurement Information System Preference Score (PROPr) are new health state utility (HSU) scores for quality-adjusted life years in cost-effectiveness analyses. Both are expected to measure HSU more comprehensively than existing measures in cancer patients by including cancer-related health domains such as fatigue. The aim of this study is to compare both scores in a sample of breast cancer patients. METHODS: We collected QLU-C10D and PROPr from 291 patients 90 days after treatment in the outpatient clinic of the breast cancer center at Charité - University Medicine Berlin between June 2018 and April 2021. We assessed both scores' convergent and known-groups validity, agreement, and ceiling and floor effects. RESULTS: The mean QLU-C10D score [0.71, 95% confidence interval (CI) 0.69-0.74] and the mean PROPr score (0.43, 95% CI 0.41-0.46) differed systematically (0.28, 95% CI 0.27-0.30) and showed fair agreement (intraclass correlation coefficient 0.46, 95% CI 0.32-0.57). The Pearson correlation coefficient was 0.83 (95% CI 0.79-0.86). Both scores showed similar discrimination across known groups of age, treatment, cancer stage, marital status, and education. The QLU-C10D showed relevant ceiling effects. CONCLUSION: QLU-C10D and PROPr measure HSU differently as a result of different utility models. The choice between QLU-C10D and PROPr should be informed by context, population, disease, and treatment.