Introduction: Existing studies of the variables that can impact reading comprehension at intermediate levels of Primary Education are not entirely conclusive. The present study analyzes the contribution to reading comprehension made by domain-general skills, such as fluid intelligence (Gf) and working memory (WM), and domain-specific skills, such as accuracy and speed. Method: A sample of 98 Chilean third graders participated in the study. Measures of fluid intelligence, working memory, reading fluency (speed and accuracy) and reading comprehension were administered. Results: The study revealed the significant contribution made by the general and specific domains to reading comprehension. The unique contribution of Gf and WM to the prediction of reading comprehension was similar to that of reading speed. Accuracy was not found to make a significant contribution. Discussion and Conclusions: The implications and relevance of the findings with regard to psycho-pedagogical and educational practice at intermediate levels of Primary School are discussed.