BACKGROUND: Evaluation of the current clinical treatment of psoriasis in Switzerland remains to be measured with the parameters cost-of-illness and quality of life. Objective: To obtain data on out-of-pocket expenses, costs of outpatient/office-based care and inpatient care for psoriasis, and to extrapolate total costs by state of severity to the entire Swiss population. METHODS: 1200 retrospective surveys were distributed to patient members of the Swiss Psoriasis and Vitiligo Society, and 400 surveys to office-/hospital-based Swiss dermatologists. The reference year for data collection was 2005. Patients were stratified into three subgroups according to severity of disease. Costs of inpatient care were measured by the amount of hospital days of psoriatic patients from the Swiss Federal Hospital Statistics. RESULTS: 383 patient questionnaires, and 170 cases documented by 57 dermatologists were analyzed. Out-of-pocket expenses/costs for ambulatory care per patient and year ranged from CHF 600-1100 for mild psoriasis to CHF 2400-9900 for severe psoriasis. Including costs for inpatient care of approximately CHF 60 million, the total annual costs for psoriasis in Switzerland in 2004/5 amounted to approximately CHF 314-458 million. CONCLUSIONS: Moderate-to-severe psoriasis is associated with a significant impact on the quality of life and at least 4-fold higher costs than mild psoriasis, indicating the need for efficient control of the disease. This cost-of-illness study provides specific health economic data for future healthcare decision making, particularly with the advent of new therapeutic agents for effective psoriasis control.