The objective of the study was to demonstrate the difficulties of diagnosing the neuroendocrine tumor (NET) of the small intestine at the example of a concrete clinical case. In the case presented, clinical manifestations of the disease were nonspecific and the examination began from a low-informative method multispiral computed tomography (MSCT) without a bolus contrast study that was the reason of wrong diagnosis for 7 months. The detection of the swollen lymph node in the mesentery was interpreted incorrectly; additionally, only endoscopic investigation of the stomach and large intestine was used. By means of MSCT-angiography we succeeded to diagnose not only the lymph node conglomerate in the mesentery, but to reveal a tumor sized 915 cm in the ileac wall. Laparoscopy with lymph node biopsy after its morphological study permitted to verify the diagnosis before the surgery. To reduce the period of diagnostics of small intestinal NET, general practitioners should be informed on specific features of clinical manifestations of the disease and rational diagnostic methods. MSCT-angiography showed its efficiency in detection of small-sized small intestinal NET, and laparoscopy with biopsy of the mesentery lymph node will permit to verify the diagnosis before surgery.