Teachers are important role models for the development of professional behaviour of young trainee doctors. Unfortunately, sometimes they show unprofessional behaviour. To address misconduct in teaching, it is important to determine where the thresholds lie when it comes to inappropriate behaviours in student–teacher encounters. We explored to what extent students and teachers perceive certain behaviours as misconduct or as sexual harassment. We designed—with a reference group—five written vignettes describing inappropriate behaviours in the student–teacher relationship. Clinical students (n = 1,195) and faculty of eight different hospitals (n = 1,497) were invited to rate to what extent they perceived each vignette as misconduct or sexual harassment. Data were analyzed using t tests and Pearson’s correlations. In total 643 students (54 %) and 551 teachers (37 %) responded. All vignettes were consistently considered more as misconduct than as actual sexual harassment. At an individual level, respondents differed largely as to whether they perceived an incident as misconduct or sexual harassment. Comparison between groups showed that teachers’ and students’ perceptions on three vignettes differed significantly, although the direction differed. Male students were more lenient towards certain behaviours than female students. To conclude, perceptions of misconduct and sexual harassment are not univocal. We recommend making students and teachers aware that the boundaries of others may not be the same as their own.