Using open-ended questionnaires, two studies were conducted to explore social representations held by Korean undergraduates on children, adults and adolescents. Study 1 compared between children and adults with responses reported by 97 undergraduates(men: 28, women: 69). According to the results, characteristics of children distinctive from adults were basically personality-related and in particular, typical children were marked by high extroversion, low agreeableness, conscientiousness and culture. Further, happiness for both children and adults was determined mainly by interpersonal relationships, physical health and socio-economical status. However, good(or desirable) children characteristic of high agreeableness and conscientiousness were more similar to adults worthy of the name than to children worthy of the name. Using 57 undergraduates(men: 16, women: 41), Study 2 explored social representations of adolescents. The results indicated that overall adolescence were on the bridging state between childhood and adulthood. Happiness for adolescents, like both children and adults, was determined mainly by interpersonal relationships and socio-economical status. Finally, agreeableness, conscientiousness, self-, task- and relationship-related characteristics were involved in judging good(or desirable) adolescents. These findings were discussed in terms of features of Korean culture and human development.