This study examines the characteristics and problems found in the behaviors of Korean young children. We studied a total of 842 children (467 boys and 375 girls) in 6 day care centers and kindergartens located in Seoul: 50 aged below 3, 132 aged 4, and 280 aged 5. For instrument, K-BASC (Korean Behavior Assessment System for Children) was used which was adapted and validated by Lee et al.(2003) from BASC (Behavior Assessment System for Children) developed by Kamphaus and Reynolds (1992) to evaluate behaviors of young children aged between 2.5 and 5. Results show that mothers' educational level is positively correlated with children's attention problem and social skills. Children of working mothers showed higher social skills. First-born children showed more problems of depression, anxiety, aggression, and internalization. In terms of gender, boys were found having more problems of aggression, hyperactivity, externalization, and attention problem, while girls showed more problems of depression and atypical behavior. In terms of age, older children showed less problems of aggression, externalization, depression, atypical behavior, hyperactivity, and withdrawl. For the correlations among the attributes of problems, depression was found highly associated with internalization and externalization among both boys and girls. In particular, the attribute of hyperactivity was significantly associated with externalization. About 3 to 4% of the children were found needing special intervention for their behaviors in the future.