The purpose of this study was to investigate the relationship between positive as well as negative emotion and psychological well-being of college students mediated by cognitive flexibility. Participants were 338 college students recruited from 5 colleges in Seoul and Gyeonggi-do. The Positive and Negative Emotion Scale (Lee & Lee, 2006) was used to assess positive and negative emotion. The Cognitive Flexibility Inventory (CFI: Heo, 2011) was used to examine cognitive flexibility. The Psychological Well-Being Scale (PWBS: Kim, Kim, & Cha, 2001) was used to measure psychological well-being. Data were analyzed using Cronbach''s , factor analyses, frequencies, percentiles, means, standard deviations, t-tests, Pearson''s correlations and regression analyses.
The major findings were as follow:

1. In positive and negative emotion, there was no significant difference by gender. In cognitive flexibility, there was a significant difference by gender. Male students switched cognitive sets to adapt to changing environmental stimuli more easily than female students did. In psychological well-being, there was no significant difference by gender.

2. Positive and negative emotion was related to cognitive flexibility as well as psychological well-being of college students. Positive emotion was positively associated with cognitive flexibility and psychological well-being, but negative emotion was negatively associated with cognitive flexibility and psychological well-being. Cognitive flexibility was positively related to psychological well-being.

3. Positive and negative emotion influenced on psychological well-being of college students directly and indirectly via cognitive flexibility. That is to say, positive and negative emotion caused the degree of cognitive flexibility, which consequently had an impact on individual''s psychological well-being.