In spite of the fact that psychotherapy research has been conducted for a couple of decades, researchers do not share a common view on which psychotherapy effectiveness measures are the most appropriate, reliable and valid. The changing role of the patient in the treatment process, his becoming an active treatment subject, as well as accentuating the value of the opinions about psychotherapy results formulated by its different beneficiaries is a source of inspiration for a discussion about the value of the idiographic approach using patient-generated change measures of treatment effects. In this approach psychotherapy effectiveness is assessed by referring to the measures generated by an individual patient, usually individually formulated psychotherapy goals, desired effects and expectations towards treatment. What is considered to be the biggest advantage of idiographic methods using patient-generated change measures is their higher sensitivity to change detection, as well as their ability to cover change dimensions significant for the patient – which results in their higher clinical validity. At the same time, however, these methods are subject to a number of theoretical and methodological limitations, which call their usefulness into question.