This work examines the association between symbols and their representation in adult developmental dyscalculia and dyslexia. Experiment 1 used comparative judgment of numerals, and it was found that in physical comparisons (e.g., 3-5 vs. 3-5) the dyscalculia group showed a significantly smaller congruity effect than did the dyslexia and the control groups. Experiment 2 used Navon figures (D. Navon, 1977) in Hebrew, and participants were asked to name the large or the small letters. Phoneme similarity modulated performance of the control and the dyscalculia groups and showed a very small effect in the dyslexia group. This suggests that the dyscalculia population has difficulties in automatically associating numerals with magnitudes but no problems in associating letters with phonemes, whereas the dyslexia population shows the opposite pattern.