Objectives: The aim of this research was to determine the characteristics of patients with Hashimoto's thyroiditis and to determine the degree of adherence to the Mediterranean diet in the population of children and adolescents with Hashimoto's thyroiditis. Subjects and methods: The study involved 50 children and adolescents who were referred to the endocrinology clinic, Children's Clinic, KBC Split from September 1, 2022 to December 31, 2023. Standard procedures included anamnesis, clinical status, anthropometric measurements, biochemical tests, ultrasound examination of the thyroid gland, and completion of a dietary questionnaire (KIDMED). Results: The largest number of respondents, 30 of them (60%), showed an average adherence to the Mediterranean diet. Poor adherence was shown by 17 of them (34%), and at least 3 respondents (6%) showed excellent adherence. The most common symptoms are fatigue (42%) and headache (44%). Average TSH levels were 15.26 ± 47.7 mIU/L, while average FT4 levels were 13.61 ± 2.89 pmol/L. Conclusion: This study showed mostly average to poor adherence to the Mediterranean diet in the population of children and adolescents with Hashimoto's thyroiditis. Further research is needed to fully clarify the role of the Mediterranean diet in the pathophysiology of the onset and progression of Hashimoto's thyroiditis.