The purpose of this study is to investigate the effect of motivations for using smatphones and tablet PCs on using applications. For this purpose, this study took a survey targeted for smartphone and tablet PC users. The results suggested that the motivations were consisted of four dimensions ; informations, communication, specific functions and relaxation. In terms of motivations, smartphone users preferred to use specific functions and tablet PC users preferred to use them for relaxation. The motivations for using applications were depended on types of applications. Smartphone users preferred communication applications to information or entertainment ones but tablet PC users preferred entertainment and information applications to communication ones. The results also suggested that motivations for using smartphone and tablet PC had strong impact on using applications in part. The motivations for using smartphone and tablet PC worked as a strong factor for using applications. Especially, the motivations of using smartphone had a strong positive relationship with using applications.