Survival of all non-small cell lung cancer (NSCLC) patients is disappointing, with a 5-year survival of 18%. Staging NSCLC patients is crucial because it determines the choice of treatment and prognosis. Clinical staging is a complex process that comes with many challenges and with low accuracy between the clinical and pathological stage. Treatment modalities for stage I-III NSCLC consist of surgical resection, radiotherapy and chemotherapy. This review describes the current evidence on staging and the implications on adjuvant chemotherapy. For stage I disease, staging is most accurate. Primary treatment consists of surgery or stereotactic ablative radiotherapy. When a patient has stage II disease, staging is less accurate because more diagnostic modalities are necessary to stage the mediastinal lymph nodes. Surgery remains the primary treatment modality and platinum-based adjuvant chemotherapy gives a 4% 5-year survival benefit. Staging patients with stage III disease is difficult because of the heterogeneity of the patients. It should be decided if a patient has potentially resectable disease with or without risk of incomplete resection. Induction therapy with chemo(radio)therapy followed by surgical resection or definitive chemoradiotherapy are the treatments of choice. The 5-year survival can reach 44% in selected patients. Decisions in staging and treating patients with NSCLC should be made by a multidisciplinary team with sufficient expertise in all aspects of staging and treatment.