PURPOSE: This study aimed to investigate the factors influencing long-term outcome after treatment in patients with pulmonary metastasis from papillary thyroid carcinoma. METHODS: Of the 2, 832 patients with papillary thyroid carcinoma who underwent thyroidectomy at Yonsei University Medical Center from 1986~2003, 51 patients were identified to have a pulmonary metastasis. A retrospective review of 51 patients was done through medical records. RESULTS: The study group comprised 25 females and 26 males. The mean age at primary diagnosis was 45 years (range, 8~79 years). Mean follow-up was 36 months after diagnosis of pulmonary metastasis. Disease-specific survival rates at 5 and 10 years were 81% and 48%, respectively. By univariate log-rank survival analyses, age at diagnosis, postoperative radioactive iodine treatment, metastasis at diagnosis, multiple organ involvement, uptake of radioactive iodine by pulmonary metastasis and high dose of radioactive iodine treatment were significant. However, by multivariate Cox-regression analyses, age at diagnosis and high dose of radioactive iodine treatment were proven to be significant influencing factors for survival. CONCLUSION: Young age at diagnosis and high dose of radioactive iodine treatment are the most significant prognostic factors positively influencing survival in patients with pulmonary metastasis from papillary thyroid carcinoma.