A wide share of secondary school children does not reach the expected competence level in reading. These children could benefit from more efficient intervention responses, providing a better understanding of their cognitive weaknesses/deficits. Our aim was to explore the cognitive heterogeneity of a population of poor readers identified from a large sample of 948 sixth-grade children. We first assessed the contribution of phoneme awareness (PA), rapid automatized naming (RAN), and visual attention span (VAS) to reading performance in a subset of 281 children including poor and average readers/spellers. We show that all three skills are unique and significant predictors of reading fluency. We then restricted the analysis to participants with normal Raven's score (IQ) and oral language skills to focus on 110 children with more specific reading difficulties. A unique VAS deficit was found in 18% of these poor readers while 20% and 15.5% showed a unique PA or RAN deficit. Children with multiple or no deficit were further identified. The overall findings provide evidence for a variety of cognitive profiles in poor readers. They suggest that, in addition to PA interventions, training programs targeting VAS might be useful for the nontrivial share of poor readers who exhibit a VAS deficit.