Abstract Background: Celiac disease is an autoimmune disease that results from the interaction of genetic, immune and environmental factors. According to 2020 ESPGHAN guidelines, an elimination diet (i.e. excluding products that may contain gluten) is the basic method of treating celiac disease. Following a gluten-free diet is extremely problematic and patients often make unconscious deviations from the diet. Objective: The aim of the study was to asses the frequency of conscious diet mistakes and unconscious deviations from the gluten-free diet in a group of patients with long-standing celiac disease and their impact on the frequency of typical and atypical symptoms Methods: The study included 38 patients, 30 women and 8 men with a verified diagnosis of celiac disease. The effectiveness of the gluten-free diet was assessed in all participants. Blood was collected to determine IgA anti tissue transglutaminase II antibodies and IgG antibodies against deamidated gliadin peptides by ELISA. All survey participants provided data concerning current gastrointestinal and systemic symptoms, bowel habits, comorbidities, dietary habits, physical activity and socioeconomic conditions. Results: 25 patients (65.78%) declared strict adherence to the gluten-free diet. However, in this group, 7 (18.4%) patients had significantly increased levels of anti-tTG antibodies (mean 82.3 RU/ml ±78.9 SD at N