A relative agreement on the Five-Factor Model to summarize the organization of personality traits in adults in many countries and language communities has been established (e.g., McCrae & Costa, 1997). Although the model has its critics, its value has also been enhanced when developmental precursors of the five domains were identified. In addition to Digman's work (1963, 1989), recent studies of children living in different societies provide compelling evidence that children are perceived by adults in terms of traits that are markers for the general FFM (e.g., Kohnstamm et al., 1998). This presentation will focus on personality trait research in children and early adolescents with a special attention to ongoing studies in Slovenia. Strategies to assess personality in non-adult age groups are reviewed and the free descriptive strategy is emphasized: (a) findings suggest that adults describe even infants/toddlers in terms that are predominantly categorized into the FFM taxonomy and distributions of descriptors show developmental patterns; (b) based on parental free descriptions of children across countries, ecologically valid assessment tools were created. The ICID (Halverson et al., 2003) is also conceptualized as an age and culture neutral instrument, it is widely used in Slovenia and is currently being normed. Several aspects of consistency in personality traits from early through middle childhood using the ICID, longitudinal and multiple-informant approach will be presented (structural, normative, rank-order, ipsative), as well as the aspects of consistency across contexts/informants. Cross-sectional studies on ratings of 3- to 14-year-olds provide information on age, sex, and culture differences in child personality trait expression. In addition to the trait-centered approach, results based on the child-centered approach suggest 3 to 4 internally replicable personality types. The predictive validity of traits vs. types will be discussed from a developmental perspective. Concurrent and longitudinal predictive value of child/adolescent traits was found for several outcomes: emotional and social adjustment, sibling relationships, differential parenting, academic skills, academic motivation and achievement. Prospects for future research on personality development will be discussed, including assessment, at risk samples, preventing behaviour problems, and promoting competence.