BACKGROUND: In the XXI century, the frequency of pancreas diseases increased 2–3 times. The expectation that causes a pandemic lead to the development of a number of diseases. The results of studies on the relationship of overweight, obesity with the risk of developing pancreas diseases (acute pancreatitis (AP), chronic pancreatitis (CP) and pancreas cancer (PC)) are very heterogeneous (for AP and PC) and not numerous (for CP). AIMS: to identify the frequency of obesity in AP patients (APр), CP patients (СPр) and PC patients (PCр) and compare these parameters. MATERIALS AND METHODS: at the observational multicenter clinical cross-sectional uncontrolled case-study 44 APp, 97 CPp and 45 PCp were examined; the groups were comparable by sex/age. Informed consent form for participate in the study was obtained from all patients. The main outcome of the study: the frequency of obesity in APp, CPp; PCp. RESULTS: The frequency of obesity in APp (13,6%), CPp (24,7%) and PCp (20,0%) did not differ significantly. Among the examined patients, the lowest average BMI (24,2±0,7 kg/m2) was observed in APp (p=0,049). BMI ≥22,5 kg/m2 was found to be associated with AP (OR=0,398; 95%CI 0,195–0,812; p=0,011). An inverse relationship was shown between the BMI and “definite” CP (Exp (B)=0,772; 95%CI 0,632–0,942; p=0,011). In men with CP and in CPp alcoholic etiology, weight deficit was observed significantly more often than in women with CP and in CPp biliary etiology, respectively. Earlier (a year before the present survey), obesity was more common in PCp (55,6%) than in APp (13,6%, χ2=3,3; p=0,000) and CPp (25,8%, χ2=12,0; p=0,001). A history of obesity (in our study one year before PC detection) and PC (OR=4,435; 95% CI 2,180–9,025; p=0,000) direct relationship was shown. CONCLUSIONS: the frequency of obesity in APp, CPp and PCp was similar. The average BMI was higher in APp, than in CPp and PCp. BMI≥22,5 kg/m2 was a protective factor for AP. BMI was inversely associated with “defined” CP. A history of obesity was directly associated with PC. © Endocrinology Research Centre, 2020.