OBJECTIVES: The purpose of this study is to calculate WTP of caregivers with asthmatic children and compare the results of survey for WTP in 2004 and 2008. Additionally the marginal WTP for an improvement in efficacy was analyzed. METHODS: Forty-five and 60 caregivers with asthmatic children were recruited for the study enrollment with the support of Korean asthma allergy foundation in 2004 and 2008. Patients are divided into three groups according to the severity of disease assessed a patient’s FEV1 based on the patients’ medical record; mild, moderate and severe. To measure willingness to pay for treatment of asthma, three methods, binary contingent valuation question, open-ended question and bidding game were used in this study. RESULTS: Willingness to pay of caregivers with asthmatic children has increased according to the severity of the disease in both two years. The adjusted average WTP of the caregiver (US$350/year) in 2008 was higher than that of 2004 ($224/year). The yearly average WTP of caregiver in 2004 was $187 and $302 for mild and severe asthma, respectively, while that of the caregiver in 2008 was $280 and $375 for mild and severe asthma, respectively. Those were higher than adult patients’ WTP in Korea. CONCLUSIONS: WTP of caregiver with children in Korea highly related to severity of disease.  From the findings in this study, the caregiver of children with asthma has higher willingness to pay for treatment their children’s disease than adult patients.