INTRODUCTION: Separate tumor nodules with the same histology occur in the lungs in a small proportion of patients with primary lung cancer. This paper addresses how such tumors can be classified to inform the 8(th) edition of the anatomic classification of lung cancer. Separate tumor nodules should be distinguished from second primary lung cancer, multifocal ground glass/lepidic tumors and pneumonic-type of lung cancer, which are addressed in separate analyses. METHODS: Survival of patients with separate tumor nodules in the IASLC database were analyzed. This was compared with a systematic literature review. RESULTS: Survival of clinical stage patients decreased according to the location of the separate tumor nodule relative to the index tumor (same-lobe > same-side > other-side) in N0 and N-any cohorts (all M0 except possible other-side nodules). However there was also a decrease in the proportion of patients resected; among only surgically resected or among non-resected patients no survival differences were noted. There were no survival differences between same-lobe nodule patients and those with other T3 tumors, between same-side nodule patients and those with T4 tumors, and other-side nodule patients and those with other M1a tumors. The data correlated with that identified in a literature review. CONCLUSIONS: Tumors with same-lobe separate tumor nodules (of the same histology) are recommended to be classified as T3, same-side nodules as T4, and other-side nodules as M1a. Thus, there is no recommended change between the 7(th) and 8(th) edition of TNM classification of lung cancer.