Artificial intelligence (AI) and cybersecurity are in-demand skills. Despite this demand, little is known about what factors influence computer science (CS) undergraduate students’ decisions on whether to specialize in AI or cybersecurity and how these factors may differ between populations. In this study, we interview undergraduate CS majors about their perceptions of the fields of AI and cybersecurity. Qualitative analyses of these interviews show that students have narrow beliefs about what kind of work AI and cybersecurity entail, the kinds of people who tend to work in these fields, and the potential societal impact AI and cybersecurity may have. Specifically, students tended to believe that working in AI requires math and training models, while cybersecurity consists of low-level programming; that innately smart people work in both fields; that working in AI comes with ethical concerns; and that cybersecurity skills are important in contemporary society. Some of these perceptions reinforce existing stereotypes about computing and may disproportionately affect the participation of students from groups historically underrepresented in computing. Our key contribution is identifying beliefs that students expressed about AI and cybersecurity that may affect their interest in pursuing the two fields and therefore may inform efforts to expand students’ views of AI and cybersecurity. Expanding student perceptions of AI and cybersecurity may help correct misconceptions and challenge narrow definitions, which in turn can encourage participation in these fields from all students.