The purpose of this paper is to capture the pedagogical content knowledge (PCK) of university professors about quantum chemistry. More specifically, we aimed to identify and analyze relationships between specific PCK components, using an adapted version of the model of PCK of Magnusson "et al.". A sample of university professors (n = 6) who teach quantum chemistry at undergraduate level was interviewed. Data analysis combined a quantitative and qualitative methodology. Relationships were found between components of the Magnusson model, in particular, between specific orientations to teaching science, and knowledge of instructional strategies. In addition, relationships were found between teachers' knowledge of student learning, and their curriculum. In short, given their view that the learning of quantum chemistry presents many difficulties to students, most teachers combined a didactic view of teaching with an instructional approach focusing on problem solving. Taking the results of the study together, they explain what teachers do to teach quantum chemistry, and why, and therefore, the results help us to portray their PCK. (Contains 1 note, 2 tables, and 3 figures.)