Background: Clostridioides difficile, as the main cause of infectious diarrhoea in hospitalised patients, is a considerable challenge for medical personnel (hospital environment) who have direct contact with the patient, as well as being of interest to public health specialists. Financial issues related to the occurrence of the above-mentioned micro-organism are being increasingly raised. Due to the scale of the phenomenon, we are beginning to pay attention to the significant system costs caused by the diagnosis and treatment of CDI infection and its complications. Studies indicate that the nosocomial infection of C. difficile complicates hospitalisation, by increasing the cost by more than half and extending patient’s stay by an average of 3.6 days. Material and methods: The aim of this study was to attempt to calculate the estimated costs associated with the prolonged hospitalisation of patients with nosocomial CDI infection, using the example of a hospital in Lodz. A total of 53 completed hospitalisations of patients treated in the period of January–August 2018 were analysed, during which hospital Clostridioides difficile infection was identified. For the purposes of this study, statistical data collected in the hospital’s IT system were also analysed, covering 44,868 hospitalisations in the Jan–Aug 2018 period, during which no hospital infection occurred. They was a control group, in which the analysed cases were compared. The obtained data in the study determined how long each patient with Clostridioides difficile infection stayed in the hospital (from the moment infection was diagnosed until the day of hospital discharge), and which diagnosis related groups (DRG) (according to National Health Fund guidelines) were assigned. The average length of patient stay without infection within a given DRG group in each hospital ward was also determined. The collected materials became the initial point for the final analysis of hospital costs and the length of hospital stay caused by Clostridioides difficile infection. Results: Clostridioides difficile infection extended the hospital stay by an average of almost 12 days. The average cost of prolonged hospitalisation due to CDI infection (according to the average cost per person-day) was about PLN 7148 (1664 EUR), which gave a total value of about PLN 378,860.6 (88,240.5 EUR) in the examined period. At the same time, the average expenditure from the National Health Fund for hospitalisation due to CDI infections increased by about PLN 6627 (1542.8 EUR), which in the analysed period translated into over PLN 351,232.0 (81,505.5 EUR) (according to settlements with the National Health Fund). The outcome indicates that there is a clear relation between CDI and the anticipated length of hospitalisation of patients without an infection.