Abstract Numerous adverse health consequences arise from tobacco and alcohol use, though the pathways of tobacco and alcohol use from early adolescence into adulthood and the factors that best predict these pathways are not well understood. Individuals diagnosed with Attention Deficit Hyperactivity Disorder (ADHD) smoke and use alcohol at higher proportions than those without ADHD. Moreover, ADHD symptoms (i.e., hyperactivity- impulsivity [HI], inattention [IN]) below the threshold necessary for clinical diagnosis increase the risk of cigarette smoking. A clearer understanding of the developmental relationship between these symptom domains and substance use has the potential to elucidate the potential etiology of smoking and problem drinking as well as inform treatment and prevention approaches in both clinical groups and in the general population. Using traditional and innovative/advanced analytic methods for identifying population subgroups and dynamic properties of substance use (factor mixture modeling, latent curve modeling, and growth mixture modeling), we will analyze extant longitudinal data that contains information on history of HI and IN symptoms and tobacco and alcohol use outcomes. Two nationally representative databases will be used (The National Longitudinal Survey of Adolescent Health-Add Health and Panel Survey of Income Dynamics - Child Development Supplement/Transition to Adulthood - PSID-CDS/TA). The investigative team has expertise in the areas of ADHD, addiction, behavioral epidemiology and longitudinal data analysis and thus, is well poised to undertake the proposed research. The successful completion of this proposal will result in refined knowledge concerning the influence of HI and IN symptoms on substance use from adolescence to young adulthood. Such knowledge is necessary for effective preventive intervention planning and implementation.