Objective To investigate the patterns of intrathoracic lymph node metastasis in nonsmall cell lung cancer (NSCLC) and to provide a theoretical basis for the delineation of radiotherapy target volume.Methods A retrospective analysis was performed on the clinical data of 314 NSCLC patients after operation.Our focus was to investigate the distribution characteristics and metastatic extent of intrathoracic lymph nodes and their relationship with tumor size,pathological type,and primary site.Comparisons between groups were made by one-way analysis of variance.Results The frequencies of metastases to lymph nodes at stations 4,5,7,10,and 11 were all above 12％,while those at stations 1,2,3,6,8,and 9 were all below 12％.The lymph node metastasis rate was similar on the primary tumor site (P =0.102).The patients with T3 and T4 NSCLC had a significantly higher frequency of N2 lymph node metastasis than those with T1 and T2 NSCLC (17.0％ vs.11.6％,P =0.002) ;the patients with adenocarcinoma had a significantly higher frequency of N2 lymph node metastasis than those with squamous cell carcinoma (34.5 ％ vs.23.2％,P =0.008).Conclusions For patients with T3 and T4 NSCLC of adenocarcinoma subtype,we should highlight the lymph nodes at stations 4,5,7,10,and 11 when delineating the radiotherapy target volume after operation.