The coexistence of Hashimoto's thyroiditis (HT) and papillary thyroid carcinoma (PTC) is controversial. This study was conducted to evaluate the correlation between HT and PTC and to identify predictive factors for the coexistence of PTC and HT. A total of 922 patients underwent surgery for thyroid disorders between January 2001 and August 2005. In all, 199 patients had been diagnosed with PTC, 37 of whom had coexistent HT; in 689 patients, benign thyroid disease had been diagnosed. Patients' age and sex, as well as histopathology, tumor size, nodal involvement status, multicentricity, presence of metastasis, and serum thyroglobulin levels, were retrospectively reviewed. A significant correlation was observed between HT and PTC, although no statistical significance was noted between PTC and HT type (nodular or diffuse). Most patients with PTC+HT were female and younger (<40 y old) than those with PTC only. The rate of occult tumor in patients with PTC+HT was higher than that in patients with PTC alone. Data indicate the coexistence of PTC and HT and suggest that PTC may develop even in cases of diffuse HT. Total thyroidectomy is the surgical procedure of choice, especially in young, female patients with HT.