Inflammatory bowel diseases (IBD), including Crohn’s disease and ulcerative coli-tis, are chronic illnesses that impose a considerable economic burden on patients, health care providers, and society. As onset of IBD is typically during the working age and requires ongoing medical management, its costs extend beyond health care expenditures and have a broader societal impact, such as in reduced productivity. As IBD is becoming more prevalent worldwide, understanding its total economic bur-den is increasingly important. This thesis aimed to assess the economic burden of IBD from multiple perspec-tives, including from health care providers, patients, and from society. Key focus areas included direct medical costs, patient medication costs, and productivity losses due to absenteeism and presenteeism. The study population was collected from IBD patients who visited Turku Uni-versity Hospital during a one-year study period. A randomized half of the patients received a questionnaire, and for respondents, clinical and treatment data were col-lected and linked to their responses, enabling combined analysis of registry-based and patient reported data. The results showed that IBD generates considerable costs across all observed domains. Health care visits, drug therapies, and productivity losses each contributed meaningfully to the total burden. While a small number of patients accounted for a disproportionally large share of total expenses, the overall economic impact was widely distributed. These findings highlight the need to consider both direct and indirect costs in IBD cost evaluations. Using real-world registry and questionnaire data offered a strong basis for identifying key cost drivers and that could help guide future studies that determine cost effectiveness in drug management and to shape policy decisions.