Background: Whether lexical and sub-lexical orthographic skills relate to each other and to reading was investigated in French 3rd and 5th graders. Methods: Two homophone choice tasks were constructed (1) by manipulating the frequency of words sub-lexical features (choose the correct spelling in "boat" - "bacht" vs "yacht" - "yoat") and (2) by matching items on their sub-lexical properties ("beach" - "beech"). More, two orthographic choice tasks measured (1) sensitivity to legal versus illegal sub-lexical patterns ("rouve" - "rouvve") and (2) distributional probabilities ("doat" - "dacht"). Regular, irregular and pseudoword reading were assessed. Results/Conclusions: On the one hand, performances were higher for words with more frequent sub-lexical features, in favour of an impact of both lexical and sub-lexical skills in the homophone choice task. This effect was however significant in the grade 3 group only, revealing stronger reliance on sub-lexical orthographic knowledge during lexical retrieval in the younger group only. On the other hand, performances on orthographic choice tasks improved with grade and revealed to be higher for the task involving all-or-none patterns compared with that involving distributional probabilities. Regarding the relationships between this set of measures, the data revealed that the "purer" measure of lexical orthographic skills significantly correlated with sub-lexical skills and irregular word reading; yet none of the measures that involved sub-lexical orthographic skills correlated with reading.