Two reading literacy/text comprehension tests with different demands (on-line comprehension vs. memory-based comprehension) were administered to 6,104 15-year-old students from all German states and school types. The combined and specific effects of proximal and distal variables from small-scale psychological research as well as from large-scale educational studies on each text comprehension measure were investigated. Metacognitive knowledge, decoding speed, and the number of books at home (as an indicator for family background) were found to have specific and large effects on on-line comprehension and accounted for 46 percent of the variance with the highest effects for metacognition. Metacognitive knowledge was also highly predictive when the effects of specific prior knowledge and thematic interest on memory-based text comprehension were estimated simultaneously. In addition, students who showed relative strength in building up a coherent representation of specific texts (memory-based text comprehension) were characterised by high amounts of prior knowledge and thematic interest thereby underlining the importance of these student characteristics for learning.