Reading academic texts that include mainly university textbooks has been a challenge for EAP readers. There are various reasons for this difficulty; however, linguistic elements were investigated in this work. This work aims at finding out whether academic texts lexical richness is the main cause of their difficulty, or their syntactic complexity, whether lexical richness of the readers would be a more potent predictor of their academic reading comprehension, or their ability for processing complex syntactic structures. Results indicated that syntactic complexity could be regarded as influential as lexical richness in the difficulty of academic texts. Ability in processing complex syntactic structures can be considered as effective a predictor of academic reading comprehension as lexical richness. Therefore, lexical richness may no longer be supposed as the single predictor of reading comprehension, especially academic reading performance.