Digital technologies have the potential to increase the quality of instruction; however, using digital technologies does not necessarily guarantee high-quality teaching. Therefore, teachers need specific professional knowledge on how to use and implement digital technologies. Moreover, teachers need to know how beliefs about learning with digital technologies impact their teaching. Usually, knowledge and beliefs are assessed via self-report measures and in a subject-unspecific and isolated manner. The present study assesses biology-specific professional knowledge on the use of digital technologies (self-report and performance assessed) and beliefs together. Furthermore, these constructs were related to the quality of lesson plans on honeybees and analysed. Eighty-two biology teacher students from an Austrian university participated in the study. A path model revealed that self-assessed professional knowledge on the use of digital technologies was not a significant predictor of lesson planning quality. In contrast, performance-assessed knowledge and--to some extent--beliefs are significant predictors of the quality of lesson plans with technology integration. Thus, self-report measures on their own do not sufficiently predict the ability to engage in high-quality technology integration in the classroom.