Background: Despite an appropriate surgical treatment, half of early-stage non-small cell lung cancer patients will die due to lung cancer. The number of resected lymph-nodes and vascular invasion has proved to be a prognostic factor in other solid tumors, as well as breast and colorectal cancer. Here we evaluate their prognostic impact in the largest mono-centric series of resected non-small cell lung cancer patients. Methods:Clinical and pathological characteristics and prognostic outcomes of four hundred thirty-nine consecutive patients undergoing radical surgical resection for non-small cell lung cancer at our Institution were evaluated. Results:The multivariate analysis showed that number of resected lymph nodes, vascular invasion and sex had a prognostic impact on overall survival. The optimal cut-off number of lymph nodes with the highest sensitivity and specificity for estimating the outcome was set at ten after Receiver Operating Characteristics curve analysis. Removing ten lymph nodes in our study represents a cut-off with a significant prognostic impact particularly in resected stage II non-small cell lung cancer. Conclusions:Similarly to other cancer types (for example colorectal cancer), our results suggest that an adequate classification of non-small cell lung cancer should always include an adequate lymph nodes clearance, particularly in stage II non-small cell lung cancer. Again vascular invasion resulted independent prognostic factors for overall survival. Therefore the number of resected lymph nodes, together with vascular invasion, may also drive the selection of nonsmall cell lung cancer patients for adjuvant treatment. Lung cancer is one of more aggressive tumor. Lung tumor surgery with loco-regional lymphadenectomy represents the only way for the eradication of neoplastic disease. In particular, an adequate lymph nodes clearance, especially in stage II non-small cell lung cancer may modify prognosis.