Polarization of light is one of the topics in the Croatian high school physics curriculum. It is taught in the final year of high school education. Twenty-seven Croatian high-school students (aged 18-19 years) were interviewed after regular instruction about their understanding of polarization of light and the model of light itself. This paper reports on the observed students' reasoning strategies and conceptual difficulties. Some of the reported difficulties correspond with previously identified difficulties, but some new difficulties were also found. Students often based their explanations on the remembered but misinterpreted common schematic representations of polarization. Explanations seemed to be created on the spot, suggesting the absence of prior models of polarization.