Endoscopic retrograde cholangiopancreatography (ERCP) is a very useful procedure for the diagnosis of biliopancreatic disorders. As a mixed endoscopic and radiologic procedure, its diagnostic yield depends heavily on the quality and skillful interpretation of radiological images. Diagnostic pitfalls must be kept in mind and avoided. We report on the case of a gastrectomized patient (Billroth II), in whom the observation during ERCP of two contrast-filled cavities, suggested the diagnosis of pancreatic pseudocysts. Other imaging procedures fully ruled out this diagnosis. The cause of this diagnostic pitfall was the accumulation of contrast in the blind end of the afferent loop. Additionally, we comment on other false cystic images in the ERCP.