At a minimum, our long-term memory representations of word spellings consist of ordered strings of single letter identities. While letter identity and position must certainly be represented, it is by no means obvious that this is the only information that is included in orthographic representations, nor that representations necessarily have a one-dimensional “flat” structure. Evidence favours the alternative hypothesis that orthographic representations, much like phonological ones, are internally rich, complex multidimensional structures, though many questions remain regarding the precise nature of the internal complexity of orthographic representations. In this investigation, we test competing accounts of the internal structure of orthographic representations by analysing the perseveration errors produced by an individual with acquired dysgraphia, L.S.S. The analysis of perseveration errors provides a novel and powerful method for investigating the question of the independence of different representational components. The results provide clear support for the hypothesis that letter quantity and syllabic role information are associated with, but separable from, letter identity information. Furthermore, the results indicate that digraphs—letter pairs associated with a single phoneme (e.g., the SH in FISH)—are units of orthographic representation. These results contribute substantially to the further development of the multidimensional hypothesis, providing both new and converging evidence regarding the nature of the internal complexity of orthographic representations.