The question of how to evaluate the quality of psychological treatment concerns clients, families, and mental health professionals alike. Therapeutic success is often equated with symptom reduction or the attainment of predefined goals, yet psychotherapy research suggests a more multidimensional picture. This article examines how treatment quality can be evaluated through treatment outcomes, the therapeutic alliance, self-awareness, emotional regulation, interpersonal functioning, and the capacity to accept aspects of reality that cannot be changed. It reviews the meaning of therapeutic change, the role of acceptance, collaborative goal setting, therapist-client fit, and therapist characteristics that support effective intervention. Drawing on contemporary psychotherapy research and major theoretical approaches, the article argues that high-quality therapy cannot be judged by a single indicator but should be assessed through the interaction of outcomes, process, relationship quality, and the client's evolving experience over time.