The present study examined whether specific item characteristics, such as mode of acquisition (MoA) of word meanings, make reading comprehension tests particularly difficult for deaf children. Reading comprehension data on nearly 13,000 hearing 7-to-12-year-olds and 253 deaf 7-to-20-year-olds were analyzed, divided across test levels from second to sixth grade (not necessarily corresponding to chronological age). Factor analyses across item scores suggested that, of the determinants studied, MoA--referring to the type of information (perceptual, linguistic, or both) used in word meaning acquisition--was the only factor that contributed significantly to deaf and hearing children's reading comprehension. For hearing children, MoA influenced item scores at the third- and fourth-grade levels. For the deaf children, MoA influenced item scores through the sixth-grade level. (Contains 4 tables and 3 figures.)