Mediastinal nodal metastasis is related to poor prognosis in surgically resected non-small-cell lung cancer (NSCLC) and the prognosis becomes worse with an increasing number of nodal stations involved. However, intra-operative designation of each nodal station might be difficult and confusing because of the adjacency of the nodal stations, and this may cause inaccurate nodal staging. The new concept of a 'nodal zone' was proposed by the IASLC lung cancer staging project (IALC, International Association for the Study of Lung Cancer), and we investigated the impact of the 'nodal zone' on the survival of pathological N2 patients.