Abstract： Objective To retrospectively analyze the treatment results and side effects of postoperative chemoradiotherapy and postoperative radiotherapy of thoracic esophageal squamous cell carcinoma (EPC) with positive lymph nodes.Methods Three hundred and four patients of thoracic EPC were initially treated with three-field lymphadenectomy, with pathological positive lymph nodes and without distant metastases;and randomly divided into two groups:140 patients of the simple postoperative radiotherapy (RT) and 164 patients of postoperative chemoradiotherapy (CRT).The median total dose was 50 Gy.The regimen of concurrent chemotherapy included cisplatin and taxol, and the intermission was 21 days;the median cycles were 2.35.Results The 3-year overall survival rates were 65.7% of CRT and 52.8% of RT (χ2=6.90,P=0.009), and The 3-year disease-free survival rates were 62.5% of CRT and 52.8% of RT (χ2=4.75,P=0.029).The incidences of the supraclavicular lymph-node metastases were 1.8% and 7.1%(χ2=5.21,P=0.022), respectively;and the incidences of distant metastases were 18.3% and 27.9%(χ2=3.94,P=0.047), respectively;and the incidences of overall metastases and recurrences were 27.4% and 39.3%(χ2=4.80,P=0.028), respectively.Early side effects included granulopenia (96.3% and 32.1%,χ2=140.31,P=0.000), radiation-induced esophagitis (37.2% and 26.4%,χ2=4.01,P=0.045),and gastrointestinal toxicity (23.2% and 5.0%,χ2=19.77,P=0.000).Late side effects were 6.1% and 5.0%(χ2=0.17,P=0.678), respectively.Conclusions Postoperative chemoradiotherapy of thoracic EPC with positive lymph nodes can improve the overall survival and disease-free survival, decrease the incidence of the supraclavicular metastases, the distant metastases, the total metastases and recurrences.More severe early side effects were observed in chemoradiotherapy than in the radiotherapy group,but well tolerated.