Deaf children experience difficulties with reading comprehension. These difficulties are not completely explained by their difficulties with the reading of single short words. Whether deaf children and adults lag behind in the morphological processing of longer words is therefore examined in two experiments in which the processing of prefixes by deaf versus hearing children and deaf versus hearing adults is compared. The results show that the deaf children use morphological processing but to a lesser extent than hearing children. No differences appeared between the deaf and hearing adults. Differences between deaf children with and without a cochlear implant were examined, but no firm conclusions could be drawn. The implications of the results for the reading instruction of deaf children are discussed.