AimCOVID-19 is one of the most consequential pandemic in world history. Chronic diseases, which are risk factors that increase the case fatality rates, have been the leading cause of death all over the world. This study was aimed at detecting coexisting chronic diseases in patients hospitalized with a diagnosis of COVID-19.Material and methodThe study was carried out with data from 229 patients in an intensive care unit, from June 1st through June 30th. 2020. The inclusion criteria of the study was as follows: (1) having a COVID-19 diagnosis confirmed by PCR test; (2) being hospitalized in the relevant intensive care unit within the dates of the study; and (3) having their data accessible through the hospital automation system. Through literature; chronic diseases of the patients and their effects on the COVID-19 process were evaluated. Statistical analyzes were performed using the Statistical Package for Social Sciences (SPSS) version 24.0 (IBM Corp.; Armonk, NY, USA).ResultsThe average age of the patients studied were 61.4 years. While the average symptom duration was 8.2 days; total hospitalization period was 13.1 days. The average length of stay of patients (n = 75) who were sent to intensive care unit was 10.1. The most common chronic disease among patients was hypertension with 47.2%. This was followed by diabetes mellitus (32.8%) and heart disease (27.5%), respectively. In the population studied, cough (59.4%), fever (58.5%) and shortness of breath (45.9%) were found to be the most common symptoms. Leukopenia, impairments in liver and muscle enzymes, abnormal C-reactive protein, ferritin and d-dimer levels were the important biochemical tests.ConclusionParticular attention should be paid to the elderly COVID-19 patients with chronic diseases, especially DM, HT and cancer.