Jonas Hoffmann,1,* Burkhard Haastert,2,* Manuela Brüne,1 Matthias Kaltheuner,3 Alexander Begun,1 Nadja Chernyak,4 Andrea Icks1,4,5 1Institute of Health Services Research and Health Economics, German Diabetes Center, Düsseldorf, Germany; 2mediStatistica, Neuenrade, Germany; 3Specialized Diabetes Practice Leverkusen, Leverkusen, Germany; 4Faculty of Medicine, Centre for Health and Society, Institute of Health Services Research and Health Economics, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany; 5German Center for Diabetes Research, Ingolstädter Neuherberg, Germany *These authors contributed equally to this work Aims: Patients with diabetes are probably often unaware of their comorbidities. We estimated agreement between self-reported comorbidities and administrative data. Methods: In a random sample of 464 diabetes patients, data from a questionnaire asking about the presence of 14 comorbidities closely related to diabetes were individually linked with statutory health insurance data. Results: Specificities were >97%, except cardiac insufficiency (94.5%), eye diseases (93.8%), peripheral arterial disease (92.6%), hypertension (90.9%), and peripheral neuropathy (85.8%). Sensitivities were 90% (hypertension, myocardial infarction, and eye disease), and six were below 70%. Six negative predictive values were >90%, and two