RATIONALE: Minority patients with lung cancer are less likely to receive stage-appropriate treatment. Along with access to care and provider-related factors, cultural factors such as patients' lung cancer beliefs, fatalism, and medical mistrust may help explain this disparity. OBJECTIVES: To determine cultural factors associated with disparities in lung cancer treatment. METHODS: Patients with newly diagnosed lung cancer were recruited from four medical centers in New York City from 2008 to 2011. Using validated tools, we surveyed participants about their beliefs regarding lung cancer, fatalism, and medical mistrust. We compared rates of stage-appropriate treatment among blacks, Hispanics, and nonminority patients. Multiple regression analyses and structural equation modeling were used to assess whether cultural factors are associated with and/or mediate disparities in care. MEASUREMENTS AND MAIN RESULTS: Of the 352 patients with lung cancer in the study, 21% were black and 20% were Hispanic. Blacks were less likely to receive stage-appropriate treatment (odds ratio [OR], 0.50; 95% confidence interval [CI], 0.27-0.93) compared with whites, even after adjusting for age, sex, marital status, insurance, income, comorbidities, and performance status. No differences in treatment rates were observed among Hispanics (OR, 1.05; 95% CI, 0.53-2.07). Structural equation modeling showed that cultural factors (negative surgical beliefs, fatalism, and medical mistrust) partially mediated the relationship between black race and lower rates of stage-appropriate treatment (total effect: -0.43, indirect effect: -0.13; 30% of total effect explained by cultural factors). CONCLUSIONS: Negative surgical beliefs, fatalism, and mistrust are more prevalent among minorities and appear to explain almost one-third of the observed disparities in lung cancer treatment among black patients. Interventions targeting cultural factors may help reduce undertreatment of minorities.