Due to the distance education implemented with the COVID-19 pandemic, online synchronous education activities have started to be carried out using tools such as Zoom. In this process, students have experienced various problems and one of them is related to cyberloafing behaviors (CLB). The main purpose of this study was to examine the factors influencing CLB among Turkish adolescent students in online synchronous lessons. The research sample consisted of 570 university students. The data of the research were obtained with the scales (cyberloafing scale, Internet gaming disorder scale, smartphone addiction scale, beck depression scale, locus of control scale) that the students answered based on self-report. Structural Equation Modeling was used in the analysis of the data. Research findings show that students' depression states affect internet gaming disorder (IGD). It has been determined that IGD affects locus of control and smartphone addiction. Smartphone addiction affects students' CLB. One of the innovative aspects of our research is examining the structural relationships between IGD, smartphone addiction, and locus of control variables. This research is original research in which these variables were investigated within the scope of IGD. Another innovative aspect of the research is to examine the reasons for cyberloafing by students during synchronous lessons. It is thought that the present study will provide insights for educators and researchers in terms of revealing the causes of students' CLB in online synchronous courses, which are increasingly used in the context of both synchronous courses and hybrid courses after the Covid 19 pandemic, and discussing what can be done to overcome them.