Language comprehension is crucial to reading. However, theoretical models and recent research raise questions about what constitutes this multifaceted domain. We present two related studies examining the dimensionality of language comprehension and relations to reading comprehension in the upper elementary grades. Studies 1 (Grade 6; N = 148) and 2 (Grade 3-5; N = 311) contrasted factor models of language comprehension using item level indicators of morphological awareness and vocabulary (Studies 1 and 2) and syntactic awareness (Study 2). In both studies, a bifactor model--including general language comprehension and specific factors for each language component--best fit the data, and general language comprehension was the strongest predictor of reading comprehension. In Study 2, the morphology-specific factor also uniquely predicted reading comprehension above and beyond general language comprehension. Results suggest the value of modeling the common proficiency underlying performance on tasks designed to tap theoretically distinct language comprehension skills.