This study analyses the relationship between orthographic processing and reading skills in Spanish speaking children, taking into account school experience and different reading levels, focusing on aspects of orthographic ambiguity, frequency, semantics and efficiency in written word recognition. Lexical orthographic processing assessment measures, decoding and lexical-semantic representations for reading ability were used in a sample of 1070 years 2 to 6 primary school students. Results showed the significant contribution orthographic lexicon makes to reading proficiency in Spanish, as well as the impact students years' experience in reading practice has on specializing and refining orthographic lexicon, particularly in words with ambiguous spelling. These results are discussed in the context of orthographic transparency and interdependence between the mechanisms of grapho-phonological and orthographic-lexical word recognition.