OBJECTIVES: Patient experience and health status measures are part of surveys which are included in pay for performance approaches and public reporting. If patients are unable to respond, family members such as proxies are asked to report on their behalf. It is not known if proxy-specific information affects how proxies report on patient care experience and health status. The aim of this study was to evaluate if proxy-specific covariates impact proxy reporting of patient cancer care experience, quality, and quality of life, and determine if these covariates are important for data collection. METHODS: Secondary analysis of data from the Cancer Care Outcomes Research and Surveillance (CanCORS) study, a cross-sectional survey. Respondents were proxies for living patients with colorectal or lung cancer. Outcomes included experiences with medical and nursing care, care coordination, care quality rating, physical and mental health. All outcomes were on 0-100 scales (0=worst, 100=best). Proxy characteristics included relationship to patient, sex, education, frequency of proxy-patient contact, frequency of attending consultations, and frequency of discussing medical decisions and discussing the patients’ feelings with the patient. Analyses used linear regression models with patient sociodemographic and clinical characteristics and proxy-specific covariates. Multiple imputation was used for missing data. RESULTS: Of the 1,011 proxies, most were the patient’ spouse/partner (49%) or child (36%). Although most proxies (66.3%) always attended medical visits, a minority reported never attending (2.6%). In adjusted analyses, child proxies reported worse average care experiences and lower quality ratings than spouses (-3.5 to -8.8 points lower on average). For medical care and care coordination, proxy responses became progressively more negative as proxy frequency of attendance decreased. Proxies who never attended reported significantly worse medical care (-10.5 points, 95% CI: -18 to -3) and care coordination (-13.4 points, 95% CI -20.4 to -6.4). CONCLUSIONS:  Collection of proxy-specific covariates in surveys using proxy data is warranted.