Obstruction of the duodenum is the most common intestinal obstruction of the fetus and newborn. A typical symptom of duodenal atresia is the double bubble sign. However, in order to diagnose annular pancreas, it is also required to locate a hyperechogenic band around the double bubble. We analysed the possibility of prenatal differential diagnosis of intestinal atresia, such as duodenal atresia and annular pancreas based on the analysis of two cases examined in the 26th week of pregnancy. This material was analysed by two ultrasonographers (one pediatric surgeon). Conclusions: "Double bubble" symptom in prenatal sonography is typical of high level intestinal obstruction, but it can occur both in classical duodenal atresia, and in the cases of annular pancreas, and in other rare anomalies. Classic prenatal ultrasound examination using 2D option seems to be insufficient for accurate differential diagnosis.