Purpose: To assess the impact of EQ-5D country-specific value sets on cost-utility outcomes. Methods: Data from 2 randomized controlled trials on low back pain (LBP) and depression were used. 3L value sets were identified from the EuroQol Web site. A nonparametric crosswalk was employed for each tariff to obtain the likely 5L values. Differences in quality-adjusted life years (QALYs) between countries were tested using paired t tests, with United Kingdom as reference. Cost-utility outcomes were estimated for both studies and both EQ-5D versions, including differences in QALYs and cost-effectiveness acceptability curves. Results: For the 3L, QALYs ranged between 0.650 (Taiwan) and 0.892 (United States) in the LBP study and between 0.619 (Taiwan) and 0.879 (United States) in the depression study. In both studies, most country-specific QALY estimates differed statistically significantly from that of the United Kingdom. Incremental cost-effectiveness ratios ranged between €2044/QALY (Taiwan) and €5897/QALY (Zimbabwe) in the LBP study and between €38,287/QALY (Singapore) and €96,550/QALY (Japan) in the depression study. At the NICE threshold of €23,300/QALY (≈£20,000/QALY), the intervention's probability of being cost-effective versus control ranged between 0.751 (Zimbabwe) and 0.952 (Taiwan) and between 0.230 (Canada) and 0.396 (Singapore) in the LBP study and depression study, respectively. Similar results were found for the 5L, with extensive differences in ICERs and moderate differences in the probability of cost-effectiveness. Conclusions: This study indicates that the use of different EQ-5D country-specific value sets impacts on cost-utility outcomes. Therefore, to account for the fact that health state preferences are affected by sociocultural differences, relevant country-specific value sets should be used.