This study examined whether preference for solitude promotes emotional well-being after controlling for the influence of loneliness. We administered a questionnaire that included variables regarding preference for solitude, loneliness, positive affect, and negative affect. The sample consisted of 318 young adult university students and 253 individuals aged 65 and older. The results showed a significant negative correlation between preference for solitude and positive affect; however there was no correlation between preference for solitude and negative affect. Hierarchical multiple regression analysis confirmed a negative effect of preference for solitude on negative affect after controlling for the influence of loneliness, and there was no effect on positive affect. The results of this study supported the hypothesis concerning the relationship between preference for solitude and negative affect, and demonstrated that preference for solitude decreased negative affect and promotes emotional well-being.