Case Studies Within Psychotherapy Trials: Integrating Qualitative and Quantitative Methods presents a specific, mixed-methods approach, called the “Cases Within Trials” (CWT) model, to psychotherapy research, combining the results from a randomized clinical trial (RCT); the results of richly and qualitatively detailed systematic case studies involving contrasting outcomes drawn from the experimental condition of the RCT; and a synthesis of the two types of knowledge. Chapter 3 of the book applies this model to an RCT study of a group-based, cognitive-behavioral treatment (CBT)—called “Cool Kids/Chilled Adolescents”—for youth anxiety in Denmark. Finding a substantial statistical advantage of the CBT treatment to a waiting-list control condition, the authors then analyze and compare the positive-outcome case of Lisa with the negative-outcome case of Marius, both drawn from the CBT condition.