Introduction: Type1 diabetes mellitus( DM1) is frequently associated with other autoimmune diseases such as celiac disease, Hashimoto thyroiditis and vitiligo. Among children and adolescents,thyroid disease is the most common autoimmune endocrinopathy. The possibility of occult thyroid disease should be considered at diagnosis and when a patient is assessed at anual review. Objective: The aim of the study was to determine the prevalence of hypothyroidism and autoimmune thyroiditis among children and adolescents with diabetes mellitus hospitalised in pediatric clinic,during 2012-2013. Material and methods: We reviewed the medical records of 54 patients.The following parameters were the gender, age,the age at diagnosis,duration of DM1,hemoglobin A1c(Hb1c),ultrasonography evaluation, including mesurement of thyroid volume, as well as analysis thyroid peroxidase antibodies(TPO Ab),antithyroglobulin antibodies(Tg Ab), thyroidstimulating hormone(TSH) and thyroxine(T4). Results: The study included 54 patientes,43% were girls and 57% boys, aged from 2 and 18 years,HbA1C levels avereged 9,5±1,8%. Fourteen children had positive antithyroid antibodies(25%),20 were positive for Tg Ab and 5 for TPO Ab.Among children with positive antibodies,8 were in euthyroidism, 6 in hypothyroidism, subclinical in 2 and clinical in 4 patients.The prevalence of thyroiditis is higher in children with a duration of diabetes more than 5 years, eleven patients with positive antithyroid antibodies. Conclusions: The prevalence of overt hypothyroidism (7,4%), in the outcome of AIT in children with DM1 was above the population level, wich confirms the effective of evaluation of thyroid function in diabetic children.