Abstract: Objective : To analyze the modality and pattern of thoracic lymph node metastasis from lung cancer and to explore the reasonable surgical dissection extension of intrathoracic lymph nodes for patients with lung cancer. Methodse : From September 2004 to December 2006, 215 lung cancer patients were enrolled into this study. All these patients received radical resection of primary tumor and systemic intrathoracic lymph node dissection. The number of lymph nodes in each area was recorded and pathological examination was performed. The frequency of lymph node metastasis in each area, the relationship of primary tumor site, tumor size and histology with lymph node metastasis were analyzed. Results : A total of 3,680 lymph nodes were found in 1,070 areas. The average number of lymph node dissected was 17.1 for each case. A total of 468 positive lymph nodes were found in 198 lymph node groups. Intrathoracic lymph node metastases were found in 94/215 patients, with a positive rate of 43.7%. The frequencies of metastasis to the area 11,10, 7, 5 and 4 which surrounded the hilar were much higher than those to the area of 9, 6, 8, 3, 2, and 1 which were far away from the hilar. The incidence of lymph node metastasis was higher in small cell lung cancer than in non-small cell lung cancer (P<0.05). The rate of lymph node metastasis was increased with the enlargement of tumor size. Tumors located in the upper lobe had a tendency of metastasis to the upper mediastinum more frequently, while tumors located in the lower lobe had a tendency of metastasis to the upper and lower mediastinum. Conclusion : Most of metastatic lymph nodes in lung cancer follow the lymphatic drainage, that is, from intrapulmonary to the hilar and then to the mediastinum. The skip metastasis of mediastinum nodes is common. Systemic dissection of intrathoracic lymph nodes is necessary in radical surgery for lung cancer.