This study focuses on the shared variance between reading comprehension and word-level reading skills in a population of 534 Greek children in Grades 2 through 4. The correlations between measures of word and pseudoword accuracy and fluency, on the one hand, and vocabulary and comprehension skills, on the other, were sizeable and stable or increasing with grade. However, the unique contribution of word reading to comprehension became negligible after vocabulary measures were entered in hierarchical regression analyses, particularly for higher grades, suggesting that any effects of decoding on comprehension may be mediated by the lexicon, consistent with lexical quality hypothesis. Structural modeling with latent variables revealed an invariant path across grades in which vocabulary was defined by its covariation with reading accuracy and fluency and affected comprehension directly. It is argued that skilled word reading influences comprehension by strengthening lexical representations, at least when phonological decoding can be relatively effortless.