OBJECTIVES: To assess the relationship between quality of life and willingness to pay of asthma patients classified with disease severity and age in Korea. METHODS: A total of 549 Patients diagnosed asthma were recruited for this study enrollment with the support of Korean Asthma Allergy Foundation in April 2004. Patients are composed to Adults, children with asthma and the children's care giver. Severity of disease was assessed a patient's FEV1 based on the patients' medical record and classified by four groups. National approved disease specific questionnaires for adults and the care givers measured patient's quality of life. To measure willingness to pay for treatment of asthma, 3 methods, binary contingent valuation question, open-ended question and bidding game were used in this study. RESULTS: WTP has a trend of increasing in more severe patients, especially in the group of caregiver of children with asthma. Also, QOL was related to severity of asthma very much in significantly (p<0.001). QOL score of adult with asthma was better than that of the caregiver. The adjusted average WTP of the care giver ($244/year) was higher than that of adult ($174/year) for every patient. The yearly average WTP of adult was $139 and $210 for mild and severe asthma, respectively, while that of the care giver was $187 and $302 for mild and severe asthma, respectively. CONCLUSION: Both WTP and QOL were highly related to severity of disease. From the findings in this study, the caregiver of children with asthma felt that the disease sometimes make their lives more difficult and have higher willingness to pay for treatment their children's disease than adult patients.