Objective To compare the value of fine-needle aspiration cytology (FNAC),Tg,TgAb and ultrasonography (US) for the differential diagnosis of lymph node metastasis in patients with DTC after operation and radioactive iodine remnant ablation.Methods A total of 61 DTC patients with enlarged lymph nodes detected by US or physical examination after operation and radioactive iodine remnant ablation were included.FNAC was performed on the lymph nodes under US guidance within one week and the results were compared with those of Tg,TgAb and US.Final results were confirmed by comprehensive FNAC,posttreatment whole,body scan (Rx-WBS) and clinical follow-up.x2 test and Fisher's exact test were performed.Resuits Fifty-eight DTC patients had successful FNAC results,and 40 patients were confirmed as malignant and 18 as benign after overall assessment.FNAC identified 39 malignant and 19 benign cases.The coincidence rates of FNAC with postoperative pathological diagnosis and Rx-WBS for malignant cases were 100％ (20/20) and 78.9％ (15/19),respectively.For the benign cases,the coincidence rates of FNAC with clinical follow-up and Rx-WBS were 93.3％ (14/15)and 4/4,respectively.The sensitivity,specificity and accuracy were 97.5％(39/40),100％(18/18) and 98.3％(57/58) for FNAC; 87.5％(35/40),55.6％(10/18) and 77.6％(45/58) for US; 92.5％(37/40),72.2％(13/18) and 86.2％(50/58) for Tg combined with TgAb (Tg/TgAb).The accuracy of FNAC was higher than that of US and Tg/TgAb(x2 =4.336,11.697,both P＜0.05),while US and Tg/TgAb showed no significant difference (x2 =1.450,P＞0.05).Tg/TgAb and US results were consistent in 39 cases with a diagnostic accuracy of 97.4％ (38/39) verified by FNAC,while the other 19 cases with inconsistent Tg/TgAb and US results were verified as malignant in 4 cases and benign in 15 cases.Conclusions FNAC is superior to US and Tg/TgAb in the evaluation of lymph node metastasis in DTC patients after operation and radioactive iodine remnant ablation.FNAC should be recommended particularly when Tg/TgAb and US had inconsistent results.