Intestinal obstruction aggravates the prognosis of colorectal cancer (CRC) patients. The aim of this study was to carry out a comparative analysis of nutritional status and inflammatory response in CRC patients with or without intestinal obstruction. The study was carried out on 43 patients with CRC. Twenty-three of these patients had intestinal obstruction. Anthropometric measurements, serum protein content, acute phase reactants, and diagnostic and risk nutritional indices were analyzed. The presence of intestinal obstruction reduced albumin (31 +/- 5.2 vs. 36 +/- 4.2 g/l; P = 0.0025) and prealbumin (0.13 +/- 0.047 vs. 0.21 +/- 0.042 g/l; P = 0.0001) and increased C-reactive protein (49 +/- 43.8 vs. 14 +/- 16.7 mg/l; P = 0.006) and alpha1-antitrypsin (189 +/- 34.7 vs. 148 +/- 35.4 mg/dl; P = 0.0011). Intestinal obstruction was related to malnutrition (86% vs. 33%; P = 0.019) and Mullen's prognostic nutritional index (48 +/- 21.7 vs. 31 +/- 17.9; P = 0.038) in CRC patients. Mullen's nutritional risk index was inversely correlated to total cholesterol (r = -0.51; P = 0.0002) and albumin (r = -0.81; P = 0.0001). No correlation was found between Duke's tumor stages and acute phase response, inflammatory parameters, and malnutrition. In conclusion, intestinal obstruction occurred more frequently in CRC patients with malnutrition. The increased morbidity and mortality of CRC patients was also associated with acute phase response, inflammation, and low serum cholesterol and triglyceride concentration.