The aim of the study was to investigate the association between the severity of COVID-19 and various comorbidities in hospitalized patients. For this reason, patient histories of 500 patients who were hospitalized in the infectious disease hospital (Moscow, Russia) during the coronavirus pandemic were analyzed. The results showed that cardiovascular and blood diseases, diabetes mellitus, diseases of the central nervous system + psychiatric disorders, and diseases of the urogenital system were all found to be associated with a more severe disease course (X-2 = 44.404; p < 0.001; X-2=55.395; p < 0.001; X-2=19.974; p < 0.001; X-2=11.723; p=0.003, respectively), while diseases of the digestive system and liver (including viral hepatitis), HIV infection, and diseases of the respiratory system + ENT organs where not found to be associated with severity of COVID-19 (X-2=6.949; p=0.031; X-2=1.582; p=0.453; X-2=0.528; p=0.768, respectively). There was also found no association between pregnancy and severity of COVID-19 (X-2=0.705; p=0.703). The authors concluded that persons who are known to have comorbidities should take extra precautions to avoid getting infected with SARS-COV-2 since they may be at a higher risk of having a severe disease course if they get sick.