BACKGROUND: The UK National Institute for Health and Clinical Excellence (NICE) has recommended that cost-effectiveness analysis includes the EQ-5D; however, this is often not implemented in the area of mental health. AIMS: To assess the appropriateness of using the EQ-5D to measure improvements in mental health. METHOD: Seventy-seven participants with psychosis were rated according to the EQ-5D and seven measures of mental health at both pre- and post-intervention. To assess construct validity we compared the (pre-intervention) mean EQ-5D scores for those with milder and more severe scores, according to each of the seven measures. To assess responsiveness we estimated the mean EQ-5D change score for those who improved (post-intervention), according to each of the measures. RESULTS: The mean EQ-5D score was more favourable for both those with milder scores (mean difference: 0.044 to 0.301) and for those who improved post-intervention (mean change: 0.029 to 0.117). CONCLUSIONS: This suggests the EQ-5D should be considered for use in future cost-effectiveness studies in the area of mental health.