OBJECTIVES: Countries generally use their own utility tariff to convert EQ-5D-3L health states to utility scores. However, it is unclear what the impact of these country-specific tariffs on the outcome of a cost-utility analysis is. Therefore, the aim of the current study was to evaluate this issue. Because the EQ-5D-3L mainly focusses on physical aspects of HRQOL, we evaluated this using data from two studies; a randomized controlled trial in patients with a physical disorder (low back pain) and a randomized controlled trial in patients with a mental disorder (depression). METHODS: A literature search was done to identify EQ-5D-3L utility tariffs derived using the Time Trade Off method. Missing data was imputed using Multiple Imputation by Chained Equations (MICE). Incremental Cost-Utility Ratios (ICURs), cost-effectiveness planes and cost-effectiveness acceptability curves (CEA curves) were estimated. RESULTS: Thirteen utility tariffs were identified. In the low back pain study, the ICUR using the Dutch tariff was 11,600 €/QALY, and ranged from 8,278 €/QALY for the Taiwanese tariff to 18,355 €/QALY for the Polish tariff. The probability of cost-effectiveness at a ceiling ratio of 30,000 €/QALY was 0.77, and ranged from 0.61 for the Polish tariff to 0.83 for the UK tariff. In the depression study, the ICUR using the Dutch tariff was 50,574 €/QALY, and ranged from 36,124 €/QALY for the US tariff to 96,551 €/QALY for the Japanese tariff. The probability of cost-effectiveness at a ceiling ratio of 30,000 €/QALY was 0.39, and ranged from 0.30 for the Japanese tariff to 0.45 for the US tariff. CONCLUSIONS: The results show that depending on the utility tariff that is chosen, the intervention may be considered cost-effective in comparison with usual care in one country and not cost-effective in another country. This suggests that results from cost-utility analyses cannot be unthinkingly transferred from one country to another.