OBJECTIVE: We investigated the relationship between Hashimoto's thyroiditis (HT) and papillary thyroid carcinoma (PTC) in children and adolescents. PATIENTS AND METHODS: We carried out a retrospective study of thyroidectomies performed from 2004 to 2017 at The First People's Hospital and the Tumor Hospital of Yunnan Province (Kunming, China). The occurrence and features of PTC and benign thyroid disease (BTD) in children and adolescents (age <= 20 years) were compared. RESULTS: We evaluated 258 consecutive thyroidectomies. Among children and adolescents with PTC, 23 cases were histopathologically confirmed as HT. Mean tumor diameter was smaller in children and adolescents with PTC than in those with BTD. Thyroid-stimulating hormone (TSH) level was abnormally elevated in a greater proportion of children and adolescents with PTC as compared to those with BTD or youths with PTC. The proportion of thyroglobulin antibody (TGAb)- and thyroid peroxidase antibody (TpoAb)-positive children and adolescents was higher in the PTC than in the BTD group. Among children and adolescents with PTC, 23 had HT as compared to two in the BTD group. The proportion of children/adolescents with abnormally elevated TSH levels was higher for the PTC combined with HT group than for the PTC without HT group. A multivariate conditional logistic regression analysis showed that elevated TGAb was an independent risk factor for PTC in children and adolescents. CONCLUSIONS: HT is associated with an increased occurrence of PTC in children and adolescents.