Despite major advances in lung cancer diagnosis and treatment, substantial geographic and socioeconomic disparities in survival remain worldwide. In Korea—where universal health coverage and national cancer screening programs are established—regional inequalities persist, suggesting an important role of contextual socioeconomic conditions. The Regional Deprivation Index (RDI) provides a multidimensional measure of structural deprivation that may explain spatial variations in outcomes.To investigate temporal trends and regional differences in lung cancer survival across Korea from 2003 to 2020, and to quantify the contribution of contextual deprivation to survival inequalities.We analyzed data on 29,065 individuals newly diagnosed with lung cancer using the Korean Regional Cancer Registry. Survival outcomes were estimated using multilevel frailty survival models that incorporated individual-level clinical and demographic factors alongside regional-level characteristics. Contextual deprivation was measured using the RDI, a composite indicator comprising nine socioeconomic dimensions: housing environment, education, social class, elderly population share, single-person households, car ownership, housing type, household composition, and marital status. Empirical Bayesian estimation was applied to generate smoothed spatial survival estimates and to visualize variations by year, sex, age group, and cancer stage.Between 2003 and 2020, overall survival improved from 41.4% to 67.9%. However, persistent and substantial regional disparities remained throughout the study period. Each one-point increase in the RDI was associated with an approximately 3.9% decrease in survival probability. After adjusting for individual and contextual characteristics, regional heterogeneity was reduced by nearly one-third, indicating that contextual deprivation meaningfully contributed to spatial inequalities. More deprived regions consistently demonstrated lower 1-, 3-, and 5-year survival rates across all tumor stages.Even with national screening initiatives and advances in therapeutics, improvements in lung cancer survival have not been equitably distributed across regions. Contextual deprivation continues to exert a strong influence on survival disparities, reflecting enduring structural barriers within deprived communities.Addressing socioeconomic deprivation and ensuring equitable access to high-quality cancer care are essential to reducing regional survival inequalities. Policies that incorporate social equity into cancer control strategies are needed so that future advancements translate into improved outcomes for all patients.