Clinical research has yielded considerable empirical support for the efficacy of treatments for adolescent substance abuse and dependence (Dennis et al., 2003a; Liddle et al., 2001; Kaminer & Burleson, 1999; Kaminer et al., 1998; Wagner et al., 1999; Wagner & Waldron, 2001; Waldron et al., 2001). Findings from controlled clinical trials have revealed consistent patterns, signaling initial, albeit preliminary, steps toward consensus regarding promising treatment models (Deas & Thomas, 2001; Liddle & Dakof, 1995; Muck et al., 2001; Ozechowski & Liddle, 2000; Stanton & Shadish, 1997; Waldron, 1997; Waldron & Kaminer, 2004; Williams & Chang, 2000). Nevertheless, this body of findings has also revealed marked individual variability in treatment response. Even within the most efficacious models, in which the majority of adolescents achieve significant reductions in substance use, reductions vary widely, and fewer than half of treated youth remains drug or alcohol free during the year following treatment (Brown, Vik, & Creamer, 1989; Dennis et al., 2003a; Spear, Ciesla, & Skala, 1999; Waldron et al., 2001; Winters, 1999). Such differential treatment outcomes point to the importance of developing and testing treatments tailored to the unique developmental needs and substance use patterns of adolescents (Deas et al., 2000; Winters, 1999). Yet, little is currently known about how substance abuse treatments work, for whom various treatments are effective, and how the durability of treatment effects over time might be enhanced.