This Special Section of the "Journal of Consulting and Clinical Psychology" focuses on research that extends beyond documenting the efficacy and effectiveness of specific psychological treatments or preventive interventions for children and youths. In the past 30 years, there have been remarkable advances in the development and evaluation of psychological treatments and preventive interventions for a wide range of child and adolescent problems. At the same time, only a small percentage of youths who suffer from emotional and behavioral problems receive psychological services, and many of these services are not evidence-based. This article discusses key features of the Special Section studies, which examine important issues related to (a) disseminating treatments in diverse community settings (i.e., investigating the transportability of treatment), (b) personalizing mental health care (i.e., investigating predictors and moderators of treatment outcome), and (c) developing evidence-based explanations of treatment (i.e., investigating mediators of treatment). Key issues that are raised in the specific studies are discussed, and important considerations for future research are highlighted. Moving the field forward requires innovation, complex research designs, and a willingness to develop treatment models that reach beyond the current body of treatment outcome and prevention research.