The 9-item Shared Decision Making Questionnaire was developed in a theory-driven manner and measures the extent to which patients are involved in the process of decision-making from the perspective of the patient (patient version SDM-Q-9) and from the perspective of the physician (physician version SDM-Q-Doc). The measure was developed for use in research and clinical practice. Both versions can equally be implemented for purposes of evaluation and quality improvement in health care. The measures should only be applied in the case of preference-sensitive decisions – i.e. when there are several treatment options for a particular disease.