Objective: The aim of the study was to determine the levels of NT-proBNP in hospitalised patients. Furthermore, the aim was to determine the connection between concentration of NTproBNP and the diagnosis of patients as well as to determine the connection between NTproBNP and some of the most relevant clinical characteristics of patients. The study design: Cross-sectional research. Participants and methods: The participants were patients hospitalised at the Department of cardiovascular disease of UHC Osijek during a period of one month. Patients who did not have complete information for this research were excluded. The method of determining NT-proBNP was ECLIA. The basis of the method is a sandwich with two monoclonal antibodies. All data was collected through the hospital information system without any contact with patients or any change in their medication or treatment. Results: It was determined that 101 of 121 patients has elevated concentration of NT-proBNP. Kruskal–Wallis test showed a difference between NT-proBNP concentration and EFLV, GFR and age. Spearman correlation test showed that there is an association between lower concentration of NT-proBNP and preserved EFLV. In conclusion: NT-proBNP is a good marker for heart disease. However, old age, comorbidity and therapy makes it more difficult to statistically analyse a connection between NT-proBNP and clinical characteristics in groups of patients who have more complex conditions and comorbidities, but there may be a statistically verifiable difference between groups of patients with less severe heart disease and groups with more severe disease, especially in the case of heart failure.