Difficulties in differentiation between inflammatory and neoplastic tumors of pancreas cause that the diagnostics based on image examinations requires the assessment of neoplastic markers. The aim of the paper is to evaluate the usefulness of Ca 19-9 in differentiation of inflammatory and neoplastic pancreatic tumors. Examinations were carried out on a group of healthy people (n = 32), patients with chronic pancreatitis (n = 32) and patients with carcinoma of exocrine part of pancreas (n = 32). In all examined patients Ca 19-9 concentration was measured by ELISA method. Ca 19-9 level in serum higher than the upper limit of range in reference group was noted in 46.9% of patients with chronic pancreatitis and in 90.6% in the group of patients with pancreatic carcinoma. Concentrations higher than 90 U/ml and 150 U/ml were noted in 31.3% and 15.6% patients with chronic pancreatitis respectively. Ca 19-9 concentration median in patients with pancreatic carcinoma (255.45 U/ml) was significantly higher (p < 0.001) in comparison to the level in patients with chronic pancreatitis (33.25 U/ml). Optimal dividing concentration was 150 U/ml. There was quite high percentage of false positive results. It made Ca 19-9 less useful in the differentiation between inflammatory and neoplastic pancreatic tumors. Ca 19-9 concentration measured in serum 37 U/ml was the dividing concentration in the diagnostics of chronic pancreatitis and pancreatic carcinoma. It seems to be not sufficient therefore in my opinion the level of 90 U/ml and even 150 U/ml should be considered as a dividing one.