STUDY AIM: The 8th edition of the TNM classification combined with the latest update of the S3-guideline (by AWMF/Scientific Medical Societies in Germany) on prevention, diagnosis, therapy and follow-up of lung cancer led to several changes in staging and treatment of lung cancer. The aim of this study was to identify differences in the distribution of patients due to changes from the 7th to the 8th edition that affected staging. The influence on surgical therapy will be discussed by using the recommendations of the latest S3 guideline. METHODS: Prospective analysis of all primary cases at two thoracic surgical centres in the year 2016 and follow-up in March 2019. Comparison of the 7th edition of tumour classification for lung cancer with the 8th edition, focused on changes in tumour staging and its effects on the appropriate surgical therapy according to the latest S3 guideline. RESULTS: A total of 432 primary cases comprised the study population. According to the 8th edition, 82 patients (7th edition: n = 85) in stage I, 43 (n = 49) patients in stage II, 100 (n = 91) patients in stage III and 207 (n = 207) patients are assigned to stage IV. 81 changes (18.7%) were detected (77 upgrades vs. 4 downgrades). 63 patients (14.6%) exhibited a different graduation within the stages. 18 patients (4.1%) were classified in different tumour stages. As a result, fewer patients (n = 12; 2.8%) should have surgery according to the latest S3 guidelines. 290 patients (67.1%) were classified to new subgroups (IA1-3, IIIC and IVA/B). Two-year survival was significantly higher in IVA (25.2%) vs. IVB (13.0%) patients (p < 0.05). CONCLUSION: The 8th edition of the TNM-classification affords a higher level of differentiation. In this study, the new TNM classification led to a shift in the distribution, with a tendency to increase the tumour stage. This is mainly caused by changes in the T-descriptor and stage grouping. As a result, fewer patients in stage I - IIIA should have surgery according to the latest S3 guidelines. A significantly higher two-year survival rate was detected in stage IVA (M1a and M1b) compared to IVB and justifies the new differentiation due to the metastatic pattern.