The ability of dyslexic children with or without phonological problems to process simultaneous and sequential visual information was assessed using two tasks requiring the oral report of simultaneously or sequentially displayed letter-strings. The two groups were found to exhibit a simultaneous visual processing deficit but preserved serial processing skills. However, the impairment in simultaneous processing was larger in the dyslexic group with no phonological disorder. Although sequential and simultaneous processing skills both related to reading performance, simultaneous processing alone significantly contributed to reading speed and accuracy. These findings suggest that a simultaneous processing disorder might contribute to developmental dyslexia.