Successful reading comprehension has long been known to be a complex and multifaceted process. The existing body of knowledge about early reading acquisition identifies word-level processes as the primary contributor to reading comprehension; yet much remains to be understood about what other processes impact a child’s reading ability. Cognitive models of reading comprehension, such as Kintsch’s (1998) construction-integration model, offer significant insights into the complexity of reading comprehension. Still, to date, the application of cognitive models to reading development and disability has been limited. Generally, the developmental research has constructed a model of reading based on two broad elements—word-level processes and oral language—theorizing that both factors are essential for successful comprehension. However, the constructs of both word-level processes and oral language contain many unexplored subquestions and issues regarding processes critical for successful reading comprehension. For example, what evidence do we have that reading comprehension consists of multiple processes, and which processes appear to be critical? When do different processes become more/less important? How does the measure of reading comprehension that we use influence our findings? And, finally, what are the potential explanations/origins for difficulties with reading comprehension, and how might future research address these?