The aim of this article was to deepen the reflection on the importance of decision-making in psychotherapy. As a starting point, we adopted the views of classic psychotherapists (Eric Berne, Harold Greenwald, Antoni Kępiński) who believed that the patient's decisions make a significant contribution to the formation of mental disorders and their treatment. The development and argumentation of this thesis was supported by knowledge of clinical and developmental psychology as well as clinical illustrations. In the first part of the text, we outlined a classical indeterministic perspective on decision-making and, a way of thinking about decisions based on the notion of the human condition, which is reconcilable with the determinism of psychological mechanisms and useful in psychotherapy. In the next two parts, we focused on identifying the specificities and types of decisions in the patient's life course that can generate and/or sustain psychopathology (adaptive and moral) and those that contribute to treatment (oriented towards truth-seeking and responsibility-taking). In the final section, we attempted to clarify the potential impact of the therapist's decisions on the patient's decisions that are crucial for therapeutic change and made some methodological and practical proposals.