Staging is an essential part of the approach to patients with lung cancer. The primary goal of the tumor classification is to correctly describe the anatomic extent of the disease. The anatomic extent of the tumor has a major impact on the treatment selection and prognosis. The general approach to patients with non-small cell lung cancer include mediastinal staging and non-thoracic staging methods, history and physical examination, imaging, minimally invasive techniques, and invasive surgical techniques. The current lung cancer staging system is the eighth edition of the tumor, node, and metastasis (TNM) classification, which was took effect in January 2017. In this article, staging methods and the definitions for current T, N, M descriptors and the stage groups in non-small cell lung cancer are reviewed. New definitions of T, N, and M factors seem to better indicate the most optimal treatment option for an individual patient and to better predict the survival in patients.