Objectives: According to the CONCORD-3 study, the 5-year survival rate of lung cancer patients in Finland has not improved during the twenty-first century. In the present study, we evaluated the survival trends of lung cancer patients diagnosed and treated in one of the five university hospitals in Finland to determine possible explanatory factors behind the lack of improved survival. Material and methods: This retrospective population-based study included all lung cancer patients diagnosed in Tampere University Hospital in 2007–2019 (N = 3041). The study population was divided into two subcohorts: the patients diagnosed in 2007–2012 and those diagnosed in 2013–2019. The two subcohorts were then compared to analyze the temporal changes in survival and the distribution of prognostic factors. Results: A comparison of the patients diagnosed in 2007–2012 and 2013–2019 showed that the patients’ overall survival had remained unchanged. The median overall survival was 8.7 months in the earlier subcohort and 9.2 months in the later subcohort. The respective 5-year survival rates were 16.6% and 17.8%, and these differences were not statistically significant. The proportion of stage IV patients (approximately 59% in both subcohorts) and their risk of death were similar for the two subcohorts. According to the regression analysis, male gender, advanced stage, and poor Eastern Cooperative Oncology Group performance status were independent risk factors for death, while a never-smoking status and mutation-positive disease were associated with a decreased risk of death, but only in the later cohort. Conclusion: Echoing the results of CONCORD-3, this study confirmed that the real-world survival of unselected lung cancer populations in Finland has not improved over the last 15 years, mainly because of the unchanged proportions of patients with late-stage lung cancer. This calls for earlier recognition of lung cancer, achieved by screening and increasing awareness of the disease.