In this paper we describe the development and first evaluation of a tool to measure children’s conceptions about the Internet. The tool uses worksheets with concept cartoons and can both serve as a formative assessment tool for classroom teachers to find their students’ difficulties and strengths on the subject and to adopt their teaching accordingly as well as a summative assessment tool for research purposes. We briefly present the data collection methods of a pilot study and the preliminary conclusions about children’s conceptions of the Internet. Moreover, we describe the challenges that we observed in measuring children’s conceptions of the Internet using concept cartoons. Finally we discuss the potential of this tool in research and classroom settings for a large scale study.