Purpose/Hypothesis: Professional behaviors are the interpersonal skills central and necessary to perform the work of a given profession. Lapses in professional behaviors remain widespread in clinical and educational settings despite the threat of disciplinary action and educational content explicitly addressing professional behaviors. We sought to assess how traditional and non-traditional physical therapy students identify lapses in professional behaviors, how they rank their relative importance, and what example lapses they would report. We hypothesized non-traditional students would more accurately identify lapses in professional behavior and report fewer lapses in their own professional behavior than traditional students. Number of Subjects: 135 physical therapy students (89 traditional, 46 non-traditional) Materials and Methods: Participating students completed an online mixed-methods survey related to professional behaviors. Results were analyzed for differences between traditional and non-traditional students using the Mann-Whitney U test. Descriptions of lapses in professional behavior were qualitatively analyzed via triangulation across investigators to allow for identification of primary themes. Results: No statistically significant difference was found between how traditional and non-traditional students assessed professional behaviors (Z = -0.73, P-value = 0.46). Both groups reported similar frequencies of their own professional behavior lapses and similarly ranked professional behaviors by importance. Behaviors described by students as salient did not, overall, correspond to the behaviors ranked by students as most important. Six themes related to lapses in professional behavior emerged from qualitative comments: external professionalism, respectfulness, communication, relationship to learning, affective professionalism, and clinical decision making. Conclusions: Both traditional and non-traditional student groups evaluated behaviors in similar ways. Students’ rankings of ten standard professional behaviors did not correspond to the rankings of the same behaviors in the reference standard, “Professional Behaviors for the 21st Century.” Themes from student comments were notably different than the standard list of professional behaviors. Clinical Relevance: Our study has identified a perception gap between how clinicians and educators previously ranked professional behaviors and how students rank the same behaviors. Given the importance of professionalism in education and practice, educators may consider engaging with students about their perceptions of professional behaviors to most effectively facilitate development of professionalism.