With the increasing relevance of Artificial Intelligence (AI) in society, AI literacy is increasingly being integrated into K-12 education. However, students already form conceptions about modern technologies (especially AI) from their interaction with their everyday environment. In this paper, we conduct a systematic scoping review on the emerging research field of secondary school students' mental models and attitudes regarding AI. Our goal is to identify research approaches and uncover research gaps. To achieve this, we reviewed literature published within the timeframe of 2012–2022 found in the ACM, IEEE, ERIC, and Science Direct databases. In total, we identified 18 relevant papers, for which we collected and evaluated research objectives, approaches, results, and areas requiring further investigation. Our findings reveal that most of the literature examined focuses with students' attitudes toward AI and moderating variables. Additionally, there is preliminary research on the types of mental models students possess about AI. Notable research gaps include the absence of development of research instruments for surveying mental models and insufficient research into the impact of learning interventions on the construction of students' mental models.