Aim. To estimate the informative value of a noninvasive fecal (calprotectin) test in the differential diagnosis of bowel diseases. Subjects and methods. One hundred and forty-two patients who had visited their physicians with intestinal disorders (a change in stool frequency and patterns, abdominal pain) were examined in an open-label multicenter cross-sectional study. The examinees’ mean age was 35±2.43 years. Gender- and age-matched comparison groups consisted of healthy individuals and patients with irritable bowel syndrome. Fecal calprotectin (FCP) was determined using a BUHLMANN Calprotectin ELISA kit. All the patients underwent colonoscopy. Results. In the patients with organic bowel diseases (ulcerative colitis, Crohn’s disease, lymphocytic colitis, colonic diverticular disease, colonic adenomas, celiac disease), the concentration of FCP was found to be substantially higher than that in the healthy individuals and patients with irritable bowel syndrome. The highest calprotectin levels were noted in the patients with inflammatory bowel diseases. Conclusion. This study demonstrated the high diagnostic value of the calprotectin test for the differential diagnosis of organic and functional bowel diseases.