To examine the feasibility, reliability, and validity of the newly developed EQ-5D-Y. The EQ-5D-Y was administered in population samples of children and adolescents in Germany, Italy, South Africa, Spain, and Sweden. Percentages of missing values and reported problems were calculated. Test-retest reliability was determined. Spearman's rank correlation coefficients with other generic measures of HRQOL were calculated. Known groups' validity was examined by comparing groups with a priori expected differences in HRQOL. Between 91 and 100% of the respondents provided valid scorings. Sweden had the lowest proportion of reported problems (1-24.9% across EQ-5D-Y dimensions), with the highest proportions in South Africa (2.8-47.3%) and Italy (4.3-39.0%). Percentages of agreement in test-retest reliability ranged between 69.8 and 99.7% in the EQ-5D-Y dimensions; Kappa coefficients were up to 0.67. Correlation coefficients with other measures of self-rated health indicated convergent validity (up to r = -0.56). Differences between groups classified according to presence of chronic conditions, self-rated overall health and psychological problems provided preliminary evidence of known groups' validity. Results provide preliminary evidence of the instrument's feasibility, reliability and validity. Further study is required in clinical samples and for possible future applications in economic analyses.