Autoimmune pancreatitis (AIP) is a rare disease of unknown pathomechanism. It belongs to the IgG4-related disease family and responds well to steroids, although the relapse rate can reach up to 20-30%. Differentiating AIP from the more common pancreatic cancer can be very challenging. About 20% of AIP is diagnosed postoperatively during final histological examination. Each of the investigative tools can add something to the definitive diagnosis; the question remains whether it is possible to prevent an unnecessary resection. Through our case we would like to demonstrate the differential diagnostic opportunities and present the literary background of this issue. In conclusion, we can state that whenever a focal pancreatic lesion is encountered AIP should always be considered.