We investigated 2 hypotheses of a recently proposed integrative theoretical model of reading, the direct and indirect effects model of reading (DIER; Kim, 2017b, 2019): (a) hierarchical relations and (b) dynamic relations (or differential relations) of skills to reading comprehension. Students were assessed on reading comprehension, word reading, listening comprehension, working memory, attention, vocabulary, grammatical knowledge, perspective taking (theory of mind), knowledge-based inference, and comprehension monitoring in Grade 2 and again in Grade 4. Structural equation model results supported the hierarchical relations hypothesis of DIER. When a nonhierarchical, direct relations model was fitted, primarily the upper level skills (i.e., word reading and listening comprehension) were statistically significant. When hierarchical, direct, and indirect relations models were fitted, lower level skills (e.g., working memory, vocabulary) and higher order cognitive skills (e.g., perspective taking) were indirectly related to reading comprehension via multiple pathways, whereas word reading and listening comprehension remained directly related to reading comprehension. Furthermore, the magnitudes of relations varied in Grade 2 versus Grade 4 such that perspective taking (as measured by theory of mind), vocabulary, and working memory had larger effects whereas comprehension monitoring and grammatical knowledge had smaller effects on reading comprehension in Grade 4 than in Grade 2. These results provide some support for the dynamic relations hypothesis of DIER, but also suggest the complex nature of the dynamic relations as a function of development and text characteristics. [For the corresponding grantee submission, see ED602720.]