This chapter investigates the measurement of children’s time use in large-scale population surveys. Some information on children as young three years of age has been gathered in Italian time use surveys by getting parents to report on their children’s activities. There has been a study of adolescents’ activities in Wave 6 of the Millenium Cohort Study in the UK. However, the richest data comes from two longitudinal studies—the long-running Child Development Supplement attached to the Panel Study of Income Dynamics (PSID) and the Longitudinal Study of Australian Children (LSAC), popularly known as Growing Up in Australia. These longitudinal surveys provide unparalleled window on the child’s development, parental influences, transmission of advantages and disadvantages, reconciliation work and family responsibilities, and the influence of media consumption on children’s behaviours. Longitudinal survey also gathers information about some crucial outcomes. These outcome variables are unique to longitudinal survey and not normally as thoroughly investigated in other time use surveys.