To evaluate the significance of the extrathyroid extension (ETE) of papillary thyroid carcinoma at the time of diagnosis and the prognostic variables of patients, we retrospectively reviewed 1, 013 thyroid cancer patients. Of the 741 papillary thyroid cancer patients, 466 (62.9%) were categorized in clinical stage I and 114 (15.4%) were categorized in clinical stage III. Of the 114 patients in clinical stage III, 81 were female (mean age 44.4±15.7 years) and 33 were male (mean age 46.9±18.1 years). Of the clinical stage III patients, 104 patients received post-operative radioactive iodide (¹³¹I) therapy while 22patients received external radiotherapy in the neck and upper mediastinum area post-operatively. In the study, age, gender, ¹³¹I accumulated dose, post-operative serum thyroglobulin (Tg) levels, and survival rate were demonstrated to be statistically significant in the groups with no recurrence and recurrence after treatment. The average follow-up period of these patients was 6.0 years. During this follow-up period, 11 patients expired. Eight died of thyroid cancer (7.0%) and 3 died of intercurrent diseases including asthma, renal cell carcinoma and propranolol overdose. Four of the 8 patients (50%) died of airway obstruction due to cancer cell invasion. Another 4 died of distant metastases, including 2 patients with skull metastases and brain invasion. The 5- and 10-year survival rates were 0.981 and 0.956 in clinical stage I and 0.923 and 0.843 in clinical stage III, respectively. In conclusion, the survival rate of the ETE of papillary thyroid cancer was lower when compared with stage I, especially in older male patients with higher post-operative serum Tg levels.