The use and function of graphic organizers when reading expository texts was examined. In two experiments the text structure, the design of the diagram and the reading strategy instruction was systematically varied. 120 participants read an expository text on a computer, and process measures (reading time, navigation) as well as product measures (recall, sentence verification) were recorded. The findings show that graphic organizers foster comprehension when the text is well-structured and when the readers use the diagram to review main topics of the text. In this case the dynamic filtering of relevant topics in the diagram (so called „Fisheye Views“) also have a positive effect. The results are applicable to text- and graphic design in both electronic and print media, and to reading strategy instruction - specifically for the use of graphic organizers in texts.