This paper has two main goals. The first is to analyse and measure gender differences in children's and adolescents' well-being by using a capability approach. The second aim is to identify the parameters that can help design policies to improve children's and adolescents' well-being. The econometric model used is a multiple indicator multiple causes (MIMIC) model, belonging to the class of structural equation models. The estimation is done on a sample of 10- to 17-year-old girls and boys and uses micro-data from the Spanish Time Use Survey (2002–03). Results show that parents' working time, both paid and unpaid, is a determinant of children's well-being. Gender differences are also especially significant, consequently posing important policy implications.