Reading comprehension is a complex skill, which involves different cognitive processes such as monitoring, working memory, interference suppression and resolution inferences. The aim of this work is to evaluate the discriminative ability of these processes, to differentiate levels of reading comprehension, in children between 8 and 9 years of age (N = 89) of public, and private, schools, in the city of Mar del Plata, Argentina. For this, specific tests were administered to each of these processes. The results distinguished two discriminant functions; the first one was the only that distinguished between individuals with good or bad comprehension abilities. A good level of reading comprehension implied to be efficient in the use of language skills (monitoring, inference, vocabulary), and, also, having abilities of processing (working memory). In contrast, the failure in general processing skills, such as phonological working memory or deficit in the ability to relateconcepts (vocabulary), appeared to be characteristic of individuals with bad comprehension  skills.