This systematic literature review analysed the content, focus, provision, and effects of support (scaffolds) in computer environments with regard to secondary school students' reading comprehension outcomes. The relevant search terms yielded many hits (period 2000-2017); however, intervention studies regarding reading comprehension of expository texts in computer environments seemed to be rather scarce. A careful analysis of these studies revealed that most of them provided cognitive support and some provided metacognitive support. Almost all studies focused on learning products, half of them in combination with learning processes. Most studies provided support in the form of statements, often provided during the task. Both cognitive and metacognitive scaffolds in computer environments produced a positive effect on reading comprehension outcomes. However, only one of the studies provided students with motivational scaffolds. Because the details of the design and content of the scaffolds used in all studies often remained unclear, it was difficult to determine the effectiveness of specific characteristics of scaffolds in computer environments. It is suggested that researchers should be more careful and comprehensive in designing and reporting on research in this area. Recommendations for future research and practical implementations of computer environments are presented.