Background. Irritable bowel syndrome (IBS) is the most common gastrointestinal disorder that is driven by the gutbrain axis and affects 1-20% of the population. Most patients note that various foods elicit abdominal symptoms, and they eliminate these products from their diets. A diet that is low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAP) is currently one of the mainstays in IBS treatment. Objective. The aim of this study was to assess the knowledge of IBS patients about the disease, treatment and the principles of the low-FODMAP diet that can alleviate gastrointestinal symptoms. Material and methods. The participants were adults diagnosed with IBS, the inclusion criteria were: absence of comorbidities requiring an elimination diet, age over 18 years, and consent to participate in the study. The respondents filled out an anonymous questionnaire containing questions about the IBS diagnosis, disease history and treatment, as well as 45 questions assessing the participants’ knowledge about the low-FODMAP diet. Results. In 28% of the cases, IBS was diagnosed by a general practitioner; in nearly 40% of the cases – by a gastroenterology specialist; in 10% of the cases – by a dietitian, whereas the remaining respondents had arrived at the diagnosis independently or with the help of support groups for IBS patients. After diagnosis, only every fourth respondent sought treatment in a gastroenterology clinic. In the studied population, 237 of the respondents had followed to the low-FODMAP diet, and the differentiating factors were sex (p=0.002), place of residence (city with a population higher than 100,000 vs. rural area; p=0.0001) and education (university vs. vocational school p=0.0043). Respondents who had been recently diagnosed with IBS (less than 12 months vs. more than 12 months before the study) were more likely to follow the FODMAP diet. Conclusions. The surveyed population was characterized by high levels of knowledge about the low-FODMAP diet, but many respondents did not strictly comply with dietary guidelines, in particular the duration of each dietary phase. Age was significantly correlated with the respondents’ knowledge, and the participants’ familiarity with low-FODMAP guidelines decreased with age. Nutritional consultations did not significantly improve the respondents’ knowledge about the low-FODMAP diet.