This study aims to verify stability following the passage of time in the cellular phone dependency of adolescents, their peer relationships, and their school life adjustment, to verify interactions among the three variables to develop programs that can alleviate the cellular phone dependency problem of adolescents, form positive peer relationships for them, and improve their school life adjustment, and provide base material for the preparation of political measures. Data used in this study was data from the ‘Korean Children & Youth Panel Survey (KCYPS)’ conducted by the Korean Policy Research Center. Research subjects were adolescents in their 1st year of middle school, 3rd year of middle school, and 2nd year of high school who were the corresponding subjects of 1st, 3rd, and 5th year data from the panel of middle school freshmen. The first research question was, “Are the cellular phone dependency of adolescents, their peer relationships, and their school life adjustment stable following the passage of time?” The second was “Do the cellular phone dependency of adolescents, their peer relationships, and their school life adjustment interact following the passage of time?” and these research questions were analyzed using Autoregressive Cross-Lagged Modeling through SPSS and AMOS. The results of this study were as follows. First, it was verified that the three variables of the cellular phone dependency of adolescents, their peer relationships, and their school life adjustment *maintain predictable stability at values found at early points in time at later points in time. Next, with regard to interaction among the three variables, peer relationships from earlier points in time predicted school life adjustment at later points in time and school life adjustment from earlier points in time allowed for the prediction of peer relationships at later points in time, showing cross-lagged effects between the two variables.