Background: Blacks in the U.S. have higher incidence and mortality rates of lung cancer (LC) compared to whites. Previous work in small studies suggests that blacks have lower perceived risk of LC which may influence smoking cessation behavior. However, racial disparities in risk perceptions (RP) of LC and smoking related diseases (SRD) in heavy smokers have not been studied. We examined LC and SRD risk perceptions among black and white ACRIN NLST participants. Methods: The 10-item Smoking Risk Perceptions Scale (SRPS) for LC and SRD was administered to NLST participants, from 4 ACRIN sites, with a minimum 30 pack-year smoking history at 1 year following baseline screening chest x-ray or low dose computerized tomography (LDCT). We 1) validated the SRPS in black and white participants separately using exploratory and confirmatory factor analyses, 2) used 2-way ANOVAs to compare RP of black and white participants and 3) used multivariable linear regression models to identify factors associated with RP. Results: Among 1742 white and 194 black participants, the 10 SRPS items loaded onto two factors (absolute and relative risk; Cronbach’s alpha=0.92 and 0.95 for white and black participants, respectively). Black participants had significantly lower RP compared to white participants (SRPS range= 10-50, mean diff. 3.48, 95% CI 2.29-4.68, p<0.01). Factors significantly associated with lower RP in a multivariate linear regression were black race (β=4.59, p < 0.001), former smoking status (β=3.82, p<0.001), male gender (β=1.35, p<0.001), lower education (β=1.16, p =0.010), and older age (years, β = 0.15, p<0.001). Conclusions: We validated the SRPS in black and white ACRIN-6654/NLST participants. Blacks had significantly lower perceptions of LC and SRD risk compared to whites, even after adjusting for study arm, sociodemographics, and smoking status. Sociodemographic factors and smoking status were independently associated with lower RP. These findings confirm that black current and former smokers are at risk of underestimating their smoking-related risk, which may contribute to lower rates of adherence to screening and smoking cessation recommendations.