Two cases of neoplastic tumors of small intestine, operated on because of acute abdominal signs, were described. In both cases, before ultimate surgical treatment, chronic gastro-intestinal bleeding and ileus were observed. None of routine diagnostic procedures (endoscopy and angiography) diagnosed the disease. It was the radiological contrast examination of small bowel, that solved the problem. For the reason, that neoplastic tumors of small intestine are extremely rare and symptoms are not specific, results of treatment were described. Also the mistakes in diagnostic process were analysed. Malignant lesions are very rare and they are not symptomatic, those are the reasons of delayed surgical treatment. Moreover, they are more common in older age (over 60), that makes the invasive diagnostics even more difficult because of general condition and additional loads, e.g. atherosclerosis or circulatory and respiratory failure. Literature survey underlines the fact, that difficulties in the diagnostics process lead to developing of advanced stages of neoplastics disease, which are treated because of massive bleeding ileus. Often patients are hospitalized many times before the ultimate surgery, but are discharged without right diagnosis. Therefore the retrospective analysis of our cases can be useful in future for the proper interpretation of clinical signs.