Objective To explore the difference of the main clinical influence factors and 131I therapeutic effect between the elderly and non-elderly patients with lymph node metastases from differentiated thyroid cancer (LMDTC). Methods The clinical influence factors in 38 patients with LMDTC were retrospectively analyzed. The difference of 131I therapeutic effect was assessed comprehensively by detection of neck ultrasonography and CT，whole body scan with 131I and changes of serum Tg level in elderly and non-elderly patient groups. Results There were significant differences in the size of lymph node and the incidence of metastases between the two groups (P＜0.05). The total effective rate of 131I therapy were 64.7% and 95.2% in the elderly group and the non-elderly group respectively (P<0.05). No hemopoietic system damage, chronic sialadenitis and secondary tumors caused by 131I therapy were found in the follow-up period．Conclusion There are some differences in the main clinical influence factors between two groups, and 131I therapeutic effect is less prominent in the elderly group than that in non-elderly group, but 131I therapy is still effective and safe for the elderly patients with LMDTC.