Subjective well-being (SWB) has been studied among adults using a variety of selfreported methods. However, there are relatively few tests of SWB available for children. Measuring SWB is also important in the school environment, but there is no valid and reliable Hungarian test for elementary schoolchildren. The aim of the study presented in this paper was to adapt the School Children’s Happiness Inventory (Ivens, 2007) to Hungarian and to construct a shorter version of the test. A multistep test reduction yielded a 12 items version that had excellent fit measures in confirmative factor analysis and high level Cronbach’s alphas in all grade groups. The validity of the new test was confirmed by means of a mental health test also developed for children. Concordant validity was confirmed by the significant correlations between the subscales of the new test and the Flow item of the mental health test. An interesting additional result is that SWB is in a negative relationship with age among schoolchildren.