Studies found that smartphone addiction is relevant to the personality of smartphone users, especially the extroverts and introverts. However, the findings of the associations between extroverts/introverts and smartphone addiction are not consistent, and it is suggested that the inconsistency results can be relevant to the types of smartphone use. Accordingly, this study adopts the use and gratification theory as a framework to examine the relationships among extroverts/introverts, smartphone addiction, and the types of smartphone use, and the mediating effect of the types of smartphone use in the relationships between extroverts/introverts and smartphone addiction. Three hundred eighteen undergraduates were recruited to fill in a questionnaire using the purposive sampling method. Results show that both introverts and extroverts are associated with smartphone addiction. However, introverts are more likely to use smartphones for process usage but extroverts for social usage. In addition, process usage but not social usage is positively associated with smartphone addiction. Moreover, only process usage is the statistical mediator for the effects of introverts on smartphone addiction. The findings indicate that intervention programs can be developed to provide more alternative activities to reduce the dependence on smartphones among introverts to gratify their process needs.