OBJECTIVES: To identify factors affecting cost-effectiveness threshold calculation in Korea. METHODS: As a pilot study of the Korean cost-effectiveness threshold study, a survey questionnaire using EQ-5D to measure QALY improvements and WTPs in hypothetical scenarios were developed. 219 Koreans from general population were interviewed face-to-face with this questionnaire in 2009. Each person’s WTPs were asked for five scenarios chosen from each level of Korean EQ-5D tariff (KCDC): 0~0.2, 0.2~0.4, 0.4~0.6, 0.6~0.8, 0.8~1.0. The same WTP questions were repeated for the QALY improvement of a family member instead of self. The questionnaire also included questions on demographics, disease status, and a visual analog scale (VAS) measure of each scenario presented. Consistency of each respondent was checked by matching ranks of five scenarios between WTPs and QALY improvements either by VAS or KCDC tariff. The distribution of WTP values can provide random starting values for a large-scale double-bounded dichotomous choices survey in 2010. RESULTS: The WTP for an additional QALY (calculated by VAS and three existing Korean EQ-5D tariffs) was around 10-25 million KRW (9164~22927 USD, 1 USD=1150 KRW) on average for those (N=150) who passed consistency check and not under medical assistance program (zero or low copayment). The averages of WTP for a family member were 2.6-5.4 million KRW (2328~4913 USD) higher than WTP for self. Respondents from Seoul (N=112) showed significantly higher WTP averages (5-12 million KRW higher, 4103-10787 USD higher; p<0.05) than nonresidents of Seoul (N=38). The relationship between WTP and QALY improvements measured by VAS was monotonic (people more appreciate significant improvements) whereas the relationship between WTP and QALY improvements measured by Korean tariffs were highest at 0~0.2 level. CONCLUSIONS: The choice of method to calculate QALY improvement seems crucial in cost-effectiveness threshold study in Korea. Other important factors include WTP for whom and living in Seoul.