The purpose of this study was to investigate the difference in Korean 4-year-olds' cognitive
development depending on variables concerning ecological system variables, predictive influences
among these variables, and different predictive patterns between working mothers and non-working
mothers. The subjects consisted of 998 4-year-olds, derived from the Korean Child Panel data of
2012. The results were as follows: First, 4-year-olds' cognitive development was different depending
on their sex, education level of mother and father, mothers' working status, quality of home
environment, and mothers' involvement in children’s life in their institution. Second, mothers'
involvement in children’s life in their institution, children's sex, quality of home environment, and
mothers' working status predicted 4-year-olds' cognitive development. Third, there was a different
pattern of predictive influence among variables according to the mothers' working status. The
mothers' involvement in their children’s lives in their institution and children's sex was proved to be
important in both, but that was more significant in working mothers, and the quality of home
environment predicted cognitive development only in working mothers. These results were discussed
in terms of necessity of the Korean national policy to support young children's cognitive
development efficiently, especially for working mothers.