OBJECTIVE: The purpose of this study was to develop a scale to measure motivation to improve Internet addiction. Motivation is known to be important to treat Internet addiction successfully. The reliability of the scale was assessed, and its concurrent validity was evaluated. METHODS: Ninety-two adolescents participated in this study. The basic demographic characteristics were recorded and the Korean version of the Stages of Readiness for Change and Eagerness for Treatment Scale for Internet Addiction (K-SOCRATES-I) was administered. Subsequently, the Internet Addiction Improvement Motivation Scale was developed using 10 questions based on the theory of motivation enhancement therapy and its precursor version designed for smoking cessation. RESULTS: The motivation scale was composed of three subscales through factor analysis; each subscale had an adequate degree of reliability. In addition, the motivation scale had a high degree of validity based on its significant correlation with the K-SOCRATES-I. A cut-off score, which can be used to screen out individuals with low motivation, was suggested. CONCLUSION: The Internet Addiction Improvement Motivation Scale, composed of 10 questions developed in this study, was deemed a highly reliable and valid scale to measure a respondent's motivation to be treated for Internet addiction.