Background: Small cell lung cancer (SCLC) is a biologically aggressive and clinically distinct subtype of lung cancer, characterized by rapid tumor growth, early metastatic dissemination, and limited durable responses to available therapies. Although it accounts for a relatively small proportion of lung cancer diagnoses, SCLC contributes disproportionately to lung cancer mortality. Robust population-based estimates of net survival are essential to quantify the true burden of SCLC, disentangle disease-specific mortality from competing causes of death, and inform cancer control strategies, especially in settings where detailed staging and treatment data are not consistently available. Objective: To estimate age-standardized net survival for SCLC up to five-years after diagnosis and to compare survival patterns with those of lung cancer overall, stratified by sex. Methods: We conducted a population-based survival study using data from the Cali Population-Based Cancer Registry, one of the longest-standing high-quality cancer registries in Latin-America. The study included all male and female residents of Cali newly diagnosed with primary lung cancer between January-2018 and December-2022, with follow-up through December-2025. Tumors were classified according to the International Classification of Diseases for Oncology, Third Edition (ICD-O-3). Net survival was estimated at 12,24,36,48, and 60-months using the Pohar–Perme estimator, which appropriately accounts for competing mortality in population studies. Age standardization was performed using the International Cancer Survival Standard (ICSS-1). Survival estimates were stratified by tumor morphology and sex, with a specific focus on SCLC, and compared with net survival for all lung cancers combined. Results: Among 1,464 patients diagnosed with lung cancer during the study period, 140 (9.6%) were classified as having SCLC. Across all follow-up intervals, net survival for SCLC was consistently and markedly lower than that observed for lung cancer overall. At 12-months after diagnosis, age-standardized net survival for SCLC was 28.1% (95%CI: 21.0-35.6), compared with 30.7% (95%CI: 28.4-33.0) for all lung cancers. Survival among patients with SCLC declined steeply within the first two-years, reaching 17.1% at 24-months and 14.2% at 36-months. At five-years, net survival for SCLC was only 6.2% (95%CI: 2.3-12.9), representing less than half of the corresponding estimate for lung cancer overall (13.0%, 95%CI: 11.0-15.1). Sex-stratified analyses revealed higher early survival among females with SCLC: at 12-months, net survival was 39.4% (95%CI: 26.9-51.8) in females and 21.2% (95%CI: 13.5-30.1) in males. However, this advantage diminished rapidly over time, and by five-years survival was uniformly poor in both sexes (4.9% in females and 6.8% in males). In contrast, for lung cancer overall, females consistently exhibited superior net survival throughout follow-up, including at five-years. Conclusions/Implications: SCLC demonstrates extremely poor population-level survival, characterized by a rapid early decline and minimal long-term survival, substantially worse than lung cancer overall. These findings indicate that SCLC contributes disproportionately to lung cancer mortality and represents a critical unmet need in cancer control. Improving population-level lung cancer outcomes will require targeted strategies for SCLC, including earlier diagnosis, expedited access to care, and the development of more effective systemic therapies. Strengthening population-based cancer registries and long-term follow-up remains essential to monitor survival trends and guide evidence-based cancer control policies.