In this chapter, we examine adult- and child-focused models of reading with respect to cognitive processing deficits associated with low literacy. We examine influential integrative models of reading and reading comprehension. We then review the empirical literature on components of reading ability, subdivided into three categories: language general, print reading specific, and non-specific cognitive. We find that most deficits discussed in the child-focused literature are also found in studies of adults with low literacy. We conclude with a discussion of implications for adult literacy research and practice. [This chapter was published in "The Wiley Handbook of Adult Literacy."]