Adolescents recruited into the Marijuana Trial (n=69; 23 per treatment arm) and the Alcohol Trial (n=54; 27 per treatment arm) during the period of this R21 project would participate in a single neuroimaging session as soon after the intake session as possible, within 7 to 30 days. During the neuroimaging session, adolescents would make intertemporal choice decisions in a Delay Discounting task regarding gains of $100 and $1,000. Preliminary data from the Marijuana trial demonstrates significant association between performance on this behavioral delay discounting task and abstinence achieved during treatment over and above the significant effect of treatment condition. The investigators seek to understand the neural processes that underlie performance on this laboratory task, and the degree to which variation in these neural processes relates to and predicts adolescent substance abuse treatment outcomes. The conceptual framework for the proposed project is based on the neuroeconomics of addiction in general, and the competing neural systems hypothesis in particular (Bechara, 2005a; Bickel, et al., 2007; Daw, et al., 2005; Jentsch & Taylor, 1999). This behavioral choice hypothesis postulates a biased competition between an "impulsive" (or ''reflexive") neural system (including the striatum, amygdala, ventral pallidum, and related structures) and the "executive" (or "reflective") neural system (including the prefrontal cortex) in understanding patterns of suboptimal decision making among substance-dependent individuals. An overarching hypothesis is that differing responses to distinct treatment approaches (CM vs. CBT) are partially determined by the pattern of activation or functional connectivity within and across these competing neural systems. These project hypotheses would be tested by the following specific aims: