['To determine the prognostic significance of unilateral cervical lymph nodal metastasis (CLNM) in patients with inoperable thoracic esophageal squamous cell carcinoma (SCC) and to identify significant prognostic factors in these patients.', 'This retrospective study involved 395 patients with inoperable esophageal SCC treated with concurrent chemoradiotherapy. The patients were classified into three groups according to their cervical lymph node status: group A, no evidence of CLNM; group B, unilateral CLNM; group C, other distant metastases. Overall survival (OS) and progression-free survival (PFS) were calculated. Significant prognostic factors were identified using univariate and multivariate analyses.', 'The 3-year OS rates in groups A, B and C were 46.7%, 33.5% and 8.3%, respectively (p<0.001, log-rank test). The corresponding PFS rates were 40.7%, 26.4% and 4.7% (p<0.001, log-rank test). Group B had a similar prognosis to that of group A and better 3-year OS (p\u200a=\u200a0.009) and PFS (p\u200a=\u200a0.006) rates than those of group C. Multivariate analysis demonstrated that T stage, chemotherapy regimen and cervical lymph node involvement were independent prognostic factors affecting OS and PFS.'] Is unilateral cervical nodal metastasis an independent prognostic factor for esophageal squamous cell carcinoma patients undergoing chemoradiotherapy : a retrospective study?