As a result of mental health disparities between White and racial/ethnic minority clients, researchers have argued that some therapists may be generally competent to provide effective services but lack cultural competence. This distinction assumes that client racial/ethnic background is a source of variability in therapist effectiveness. However, there have been no direct tests of the therapist as a source of health disparities. We provided an initial test of the distinction between general and cultural competence by examining client racial/ethnic background as a source of variability in therapist effectiveness. We analyzed cannabis use outcomes from a psychotherapy trial (N = 582) for adolescent cannabis abuse and dependence using Bayesian multilevel models for count outcomes. We first tested whether therapists differed in their effectiveness and then tested whether disparities in treatment outcomes varied across therapist caseloads. Results suggested that therapists differed in their effectiveness in general and that effectiveness varied according to client racial/ethnic background. Therapist effectiveness may depend partially on client racial/ethnic minority background, providing evidence that it is valid to distinguish between general and cultural competence. (Contains 3 figures and 2 tables.)