BACKGROUND: Non-small cell lung cancer (NSCLC) is uncommonly diagnosed in patients younger than 50 years of age. We analyzed the California Cancer Registry (CCR) to describe epidemiologic characteristics and outcomes in this patient subset and to identify factors prognostic for cause-specific survival (CSS). METHODS: Patients diagnosed with NSCLC between 1/1/98 through 12/31/09 and reported to the (CCR) as of October 2011 were included. The primary outcome measure was CSS. Cox regression models were used to evaluate predictors of CSS in young patients with NSCLC, adjusted for potential confounders. Interaction analysis was performed between age groups (<50 vs. ≥50) and specific demographic and tumor covariates. RESULTS: We identified 132,671 lung cancer cases, of which 114,451 (86.3%) had NSCLC. Of these, 6389 (5.6%) were<50 years of age (median, 46 years). The most common histology was adenocarcinoma (3697, 57.9%). Most patients had stage III (1522, 23.8%) or IV (3655, 57.2%) disease. Fewer young patients were diagnosed in recent years (n, % of total NSCLC population of that era): 1998-2001 (2355, 6.0), 2002-2005 (2182, 5.7), and 2006-2009 (1852, 5.0), P<0.001. Multivariate analysis showed that age <50 years was an independent predictor of improved CSS (HR 0.827, P<0.001). Significant predictors of better CSS in patients <50 years included female sex, Asian or Hispanic ethnicity, lower stage, later year of diagnosis, and higher socioeconomic status, among others. Adenocarcinoma histology was not associated with improved CSS in this patient subset (HR 0.987, P=0.78). Interaction analysis revealed that Hispanic race and bronchioloalveolar histology had differential CSS outcomes dependent on age group. CONCLUSIONS: This large registry study found that age <50 years is an independent predictor of improved CSS. Variables prognostic for CSS differed somewhat from those in older patients.