Although an extensive body of empirical data supports the use of cognitive-behavioral therapy (CBT) for numerous psychological disorders, a significant number of clients fail to respond adequately to mainstream CBT approaches. Partial or nonresponse to treatment is a significant issue that affects outcome across diagnostic groups. Clinicians working within a CBT framework often encounter ambivalence, poor homework compliance, and premature treatment dropout. Furthermore, a significant number of clients refuse treatment altogether, and many who do complete a course of CBT continue to struggle with residual symptoms posttreatment, which increases the risk of relapse (Westra & Dozois, 2006). In response to these issues, researchers have sought ways of improving outcome in CBT for greater numbers of individuals (Antony, Ledley, & Heimberg, 2005). In addition to modifying existing CBT protocols, the development of a so-called third wave of CBT interventions has evolved (Hayes, Follette, & Linehan, 2004), marking what proponents consider to be an exciting paradigmatic shift. As a field, and particularly for more complex clinical populations, psychology has begun to place greater emphasis on the flexible integration of change-oriented interventions with acceptance-based approaches. For example, the development of motivational interviewing (MI; Miller & Rollnick, 2002), acceptance and commitment therapy (ACT; Hayes, Luoma, Bond, Masuda, & Lillis, 2006), dialectical behavior therapy (DBT; Linehan, 1993a), and mindfulness-based cognitive therapy (MBCT; Segal, Williams, & Teasdale, 2002) offers clinicians promising new ways of conceptualizing and approaching psychological and behavioral change across diverse clinical populations. Our goals for this chapter are twofold: First, we describe a variety of modifications to contemporary CBT protocols that may help to address poor treatment response. We discuss such topics as client suitability, treatment sequencing, enhancing homework compliance, and identifying and modifying therapist-related variables (e.g., the therapeutic alliance) that may be related to treatment outcome. Second, we describe innovative treatment strategies that are currently being added to CBT protocols to enhance treatment retention, engagement, and outcome. In many cases, data regarding these strategies are preliminary, and more research is needed to more definitively determine their effects. (PsycInfo Database Record (c) 2024 APA, all rights reserved)