The present dissertation aims to investigate preferences for health gains in terms of a quality-adjusted life year (QALY) for a mental disorder from a demand-sided perspective. As depressive disorders are estimated to be the leading cause of global burden of disease in 2030, the value placed on a QALY for depressive disorders was assessed. In Study I, a representative sample of the German general public was asked to indicate their willingness to pay for a variety of health gain scenarios, allowing comparison between the value placed on QALY gains for a depressive disorder and a heart disease. Results show that QALY gains regarding cardiovascular health were valued significantly higher. In Study II, willingness to pay for one treatment method for depressive disorders, electroconvulsive therapy (ECT), was assessed in detail, investigating the effects of individual characteristics (e.g., income, educational level and prior knowledge about ECT). Results indicate that willingness to pay and knowledge about ECT were particularly low in the German general public. Study III aimed to compare preferences regarding mental health gains elicited from the general public to those of actual patients with a diagnosed depressive disorder. Although non-patients and patient respondents did not differ in their probability of indicating a positive willingness to pay, patient respondents valued the offered health gains regarding depressive disorders significantly higher than respondents from the general public. The combined evaluation of the results supports previous findings that the value indicated for QALY gains seems to depend on a variety of factors, such as the presented illness-type, individual characteristics of the respondents and characteristics of the sample. The estimation of a uniform price threshold for a QALY might therefore not be empirically attainable.