Gastrointestinal manifestations (nausea, vomiting, diarrhoea) are the most common extrapulmonary manifestations of COVID-19 infection. Although diarrhoea may be one of the symptoms of COVID-19 infection, COVID-19 and Clostridioides difficile (CD) coinfection is the most common cause of diarrhoea in patients receiving broad-spectrum antibiotic treatment. Elderly patients who have recently been admitted to the hospital are particularly at risk for a coinfection, as was the case with Clostridioides difficile infection (CDI). Delaying an early diagnosis and course of treatment for these patients can have fatal consequences. The aim of this study was to evaluate the incidence of CDI in patients hospitalized for COVID-19 as well as the influence of the coinfection on the duration of the hospitalization and the COVID-19 outcome. In a retrospective study carried out from 25th February 2020 to 31st December 2021, medical histories of 46 patients with COVID-19/CD coinfection treated in the COVID department of Clinical Hospital Center Rijeka were analysed. Patients whose CDI symptoms started after hospital discharge (post-COVID period) were excluded from the research. The incidence of CDI among COVID-19 hospitalized patients was 4,1 times greater compared to the incidence of CDI in the total number of non-COVID-19 patients in the Clinical Hospital Center Rijeka during the same period. Most of the patients were elderly (76% older than 65 years of age). Recent hospitalization (within 60 days) was present in 50% of patients. Nearly all patients (97%) were receiving antimicrobial therapy during COVID-19 infection. The length of hospitalization in patients with coinfection was 2,6 times longer compared to COVID-19 patients who did not have CDI (25 : 9,5 days). The lethal outcome was present in 28,26% of the cases. Elderly patients with empirical antibiotic therapy, and those who have been hospitalized recently, are among the COVID-19 patients who are more likely to develop CDI. The onset and clinical course of CDI can be affected by COVID-19 infection, while CDI can also worsen the course and prognosis of COVID-19 infection.