The purpose of this paper is to estimate consumers' willingness to pay (WTP) and investigate factors that affect participation in therapy to reduce weight or prevent obesity. As for the decision to participate in obesity prevention therapy, the results show that the price charged for therapy is the key factor. Furthermore, the gender, education, income, the concern that work achievement is affected by obesity, and health condition variables are found to be important and significant determinants of the decision to participate in the therapy. The average willingness to pay for obesity reduction therapy which could reduce weight by 5 kg in 3 months is estimated to be NT$12,531 (US$362) among the sample respondents. The results of the profile analysis suggest that obese females with high education, high income, who think that obesity affects work achievement, and who have tried to control their weight are the most likely to be willing to pay the greatest amount for the weight-reduction therapy.