This study uses co-orientation theory to examine the impact of mobile phone use on relational quality across three copresent contexts. It investigates the relationship between perceived similarity, actual similarity, and understanding of mobile phone usage on relationship outcomes, and uses a new measure of mobile relational interference to assess how commitment, satisfaction, and liking are affected by perceptions of relational partners? mobile phone use. Contrary to popular belief, the results from this study of 69 dyads reveals that, at least within a sample of young Americans, failing to adhere to injunctive (i.e., societal) norms regarding mobile phone usage does not impact relational quality. Rather, results indicate that perceived adherence to participants? own internal standards?by both the participant, and the participant?s relational partner?and perceived similarity between partners were more influential.