Recent neuro-cognitive theories of dyslexia presume that all dyslexics have the same type of brain abnormality irrespective of the particular writing system their language uses. In this article, we indicate how this presumption is inconsistent with cross-linguistic investigations of reading and dyslexia. There are two main issues. First, the information-processing requirements of reading vary greatly across different orthographies. Second, it is known that even within a single orthography there are different subtypes of dyslexia. Consequentially, it cannot be the case, not even within a single orthography let alone across orthographies, that all dyslexics have the same type of brain abnormality. Neuro-cognitive theorizing about dyslexia cannot afford to ignore these issues.