ObsectIve: chronic autoimmune thyroiditis (At) is the most common cause of thyroid disease in children. the aim of the study was to define the epidemiological clinical and laboratory characteristics of children and adolescents with At. DesIGN: various parameters including thyroid ultrasonography of 228 children and adolescents aged 10.2±2.5yrs (mean±sD) with At, who attended our Pediatric endocrine Unit during a 5-year period were retrospectively analysed. resULts: 191 (83.8%) were female and 142 (62.3%) were pubertal. At At diagnosis, 130 children (57.0%) were euthyroid, 75 (32.9%) had subclinical hypothyroidism, 19 (8.3%) had hypothyroidism and 4 (1.8%) had hyperthyroidism. there was a positive correlation between thyroid stimulating hormone (tsH) levels and thyroid volume sDs (r=0.15, p=0.02). sixtythree children (28%) had a goiter and 32 (14%) had thyroid nodules. three children (1.3%) had papillary thyroid carcinoma. compared to euthyroid children, children with hypothyroidism were younger (9.2±1.8 vs 10.6±2.4yrs, p<0.05) and had higher thyroid volume sDs (3.1±1.9 vs 1.2±1.2, p<0.05) and higher prevalence of goiter [11(57.9%) vs 29(22.3%), p<0.05]. cONcLUsIONs: children and adolescents with At are mostly asymptomatic; the majority are female, pubertal and euthyroid. Hypothyroid children with At have higher thyroid volume, higher prevalence of goiter and higher antithyroid antibodies titers compared to euthyroid children. Diagnosing At at an early stage offers the opportunity for a timely intervention. the potential association of At with papillary thyroid carcinoma is an additional reason for a careful follow-up of the patients with At.