Introduction: Weight loss and stunted growth are part of the clinical picture in inflammatory bowel diseases in children and adolescents, so the use of different diets in this age group is particularly risky. Until now, it is not known whether, and to what extent, the elimination diet affects the state of nutrition or some specific nutritional deficits in affected children. Objectives: The objectives of this study were to assess the frequency of self-initiated elimination diets in children with chronic inflammatory bowel diseases and to assess their impact on the quality of diet, nutritional status and course of the disease. Subjects and methods: The research conducted was a prospective study of pairs (case-control) in newly diagnosed patients under the age of 18 compared with healthy controls and their first relatives. Results: A total of 137 children were included, of which 47 (34%) with newly diagnosed chronic inflammatory bowel disease, 70 (51%) healthy controls and 20 (15%) first relatives of the patients. Of the total number of children with IBD, 28 (60%) have Crohn's disease, 16 (34%) ulcerative colitis and 3 (6%) an unclassified form of the disease. At the time of inclusion in the study, only 5 patients (10.6%) followed one of the elimination diets (two with UC; two with IBD-U and one with CD), while at the end of the study that number increased significantly (n=20; 47.6%) (10 with CD, 8 with UC and 2 with IBD-U) (p=0.027). Average energy intake differed significantly between healthy controls and patients with chronic inflammatory bowel disease (10306±4301.8 and 8223.6±2998 kcal/day; p=0.013). Conclusion: Self-initiated elimination diets are not common in the diagnosis of inflammatory bowel diseases, however, their frequency increases significantly with the duration of the disease. Elimination diets do not have a significant impact on the intake of nutrients and the nutritional status of affected children during a one-year follow-up, provided that the children have adequate nutritional supervision.