Over the years, various psychologists have issued calls for greater attention to a science of positive psychology, which focuses on studying conditions that promote optimal human and societal development. Recent calls (e.g., McCullough and Snyder, 2000; Seligman and Csikszentmihalyi, 2000) have furthered interest in studies of the nature and determinants of the good life. Such a science, along with the creation of prevention and intervention programs informed by the expanded scientific framework, is expected to improve the quality of life for all individuals, not just individuals who are at risk or who already demonstrate psychopathological conditions. To contrast with the previous emphasis on psychopathology, the development of a positive psychology requires constructs and measures that reflect the full range of human functioning, incorporating indicators of high levels of wellness as well as psychopathological functioning. This article discusses one such construct, life satisfaction, that has been studied extensively in adulthood (see Diener et al., 1999), but which has only recently gained attention with children and adolescents (see Bender, 1997; Huebner, 1997). This article reviews life satisfaction assessment research with children and adolescents, specifically with regard to construct validity. In doing so, the following areas are addressed: models of life satisfaction; convergent validity; discriminant validity; relationships with other well-being measures; relationships with external, environmental circumstances; relationships with demographic variables; cultural factors; group differences on life satisfaction measures; predictive relationships; and stability of life satisfaction reports. Conclusions regarding the validity of the life satisfaction construct are formulated. Recommendations for future research are also discussed.