Introduction: Diabetes is a risk factor for severe COVID-course. In this one-center report, we assessed clinical characteristics and risk factors associated with unfavorable outcomes in diabetic patients (DP) hospitalized due to COVID-19. Methods: We retrospectively analyzed data from a cohort of patients with confirmed SARS-CoV2 infection admitted to the University Hospital in Krakow (Poland) , a regional reference center for COVID-19, between March 6th 2020 and May 15th 2021. The data was collected from electronic medical records. Results: We included 5191 patients, mean age 61.98±16.66 years, 2348 (45.2%) women, 1364 (26.3%) DP. DP were older as compared to non-diabetics (median age 70 vs. 62 years, IQR 62-77 and 47-72, p<0.001) with similar gender distribution. DP were characterized by higher mortality (26.4% vs. 15.6%, p<0.001) , longer hospital stay (median 15 vs. 13 days, IQR 10-24 and 9-20, p<0.001) , more frequent ICU admission (15.7% vs. 11%, p<0.001) and more frequent requirement for mechanical ventilation (15.5% vs. 11.3%, p<0.001) . When adjusted for sex and age, the relative risk for in-hospital death, ICU admission and mechanical ventilation was 1.32 (95%CI 1.13-1.54) , 1.4 (95%CI 1.17-1.69) and 1.3 (95%CI 1.08-1.57) , respectively. Multivariable logistic regression showed age, CRP and D-dimer level, history of heart failure, and loop diuretic use were associated with higher risk of death, whereas anticoagulation therapy, ACEI/sartan/mineralocorticoid receptor antagonist use and thiazide use were associated with lower risk. Conclusions: In this large COVID-cohort, DP constituted more than one fourth of hospitalized patients. Their risk of death was ca. 30% higher as compared to non-diabetics, as was the risk of other important clinical outcomes. We identified a number of clinical, laboratory and therapeutical variables associated with risk of hospital death in DP with COVID-19. Disclosure M.Kania: None. T.Klupa: Advisory Panel; Abbott, BIOTON S.A., Sanofi, Research Support; Medtronic, Speaker's Bureau; Ascensia Diabetes Care, Boehringer Ingelheim International GmbH, Eli Lilly and Company, Novo Nordisk. P.W.Witek: Other Relationship; Abbott, Berlin-Chemie AG, Boehringer Ingelheim International GmbH, Medtronic, Merck & Co., Inc., Novo Nordisk, Roche Diabetes Care, Sanofi-Aventis Deutschland GmbH. B.Katra: None. M.W.Rajzer: Consultant; A. Menarini Diagnostics, Speaker's Bureau; Bayer AG, Boehringer Ingelheim International GmbH, EGIS Pharmaceuticals, Servier Laboratories. M.Malecki: Consultant; Abbott Diabetes, Boehringer Ingelheim International GmbH, Lilly Diabetes, Novo Nordisk, Speaker's Bureau; Ascensia Diabetes Care, AstraZeneca, Bayer AG, Merck & Co., Inc., Mundipharma, Servier Laboratories. K.Mazur: None. M.Terlecki: None. Z.Chaykivska: None. M.K.Fiema: None. M.A.Kostrzycka: None. M.Kopka: None. M.Wilk: None. J.Hohendorff: Advisory Panel; Abbott. Funding The authors were supported by the Polish National Center for Research and Development grant (grant number SZPITALE-JEDNOIMIENNE/18/2020) .