Introduction. Several interactions exist between thyroid function and rheumatological disorders. Many publications explored the relationship between thyroid diseases ( and juvenile idiopathic arthritis ( However, the morphological thyroid changes in patients wi th JIA were not fully explored. In children affected by JIA the occurrence of other autoimmune diseases has been described in case reports or small case series. High resolution ultrasonography ( is the most sensitive imaging modality available for exam ination of the thyroid gland and associated abnormalities. Aim of the study. To evaluate ultrasound features of thyroid gland in patients with juvenile idiopathic arthritis. Materials and methods. Fifty five patients previously diagnosed with juvenile idio pathic arthritis according to the International League of Associations for Rheumatology Classification criteria were screened for autoimmune thyroiditis. Patients with active disease as well as those in clinical remission were included. The following varia bles were observed and studied: echogenicity, echotexture, thyroid volume in relation with age and gender. Results. Our results revealed that 65.6% of patients were girls. The mean age of the studied group was 115.45±6.9 months, the median age at diagnosis was 68.53±8.79 months and the median disease duration was 53.83±8.57 months. The most frequent types of JIA were oligoarticular ( polyarticular negative RF ( and systemic ( The ultrasound examination of thyroid gland revealed abnormalities i n 33% cases, most of them cystic changes ( and hypoechogenicity ( In 3 cases thyroid nodules were detected. 2 patients presented mean thyroid volume above 2SDS compared to their age reference values. An increased vascular flow pattern on Dopp ler examination of thyroidal gland was found in 12% of cases. Correlation and regression analysis showed low age at diagnosis and longer duration of the disease to be predictors for those thyroid disorders. Conclusions. Cystic changes of thyroid gland and hypoecogenity of thyroid tissue were the most common morphological changes in patients with juvenile idiopathic arthritis. Periodic ultrasound assessment of thyroid volume and texture are recommended in juvenile idiopathic arthritis patients to avoid compl ications.