AbstractBackgroundcognitive impairment is common among older adults, necessitating the use of collateral sources in epidemiological studies involving this age group. The objective of this study was to evaluate agreement between self- and proxy-reports of cardiovascular disorders and diabetes mellitus in a population-based sample of 80-year-olds. Further, both self- and proxy-reports were compared with hospital register data.Methodsdata were obtained from the Gothenburg H70 Birth Cohort Studies in Sweden. The study had a cross-sectional design and information was collected through semi-structured interviews in 2009–2012 from participants born in 1930 (N = 419) and their proxy informants. The National Patient Register provided diagnoses registered during hospital stays. Agreement was measured with Kappa values (K).Resultsagreement between self- and proxy-reports was substantial for diabetes mellitus (K = 0.79), atrial fibrillation (K = 0.61), myocardial infarction (K = 0.75), angina pectoris (K = 0.73) and hypertension (K = 0.62), and fair for intermittent claudication (K = 0.38) and heart failure (K = 0.40). Compared to the National Patient Register, a large proportion of those with a hospital discharge diagnosis were also self- and proxy-reported.Conclusionsproxy informants can be an important source of information, at least for well-defined conditions such as myocardial infarction, angina pectoris and diabetes mellitus.