The aim of our study was to examine the relationship between NL (Native Language: Polish) phonological processing skills (verbal and phonological short-term memory, phoneme segmentation and blending, rapid automatised naming (RAN)) and the accuracy and fluency of NL and English as a Foreign Language (EFL) word and nonword decoding and word recognition skills of Polish students with and without dyslexia. Sixty-three (45%) high school and junior high school students with and 78 (55%) without dyslexia participated. We found that dyslexia, years of studying EFL at school and privately, NL phoneme blending and RAN predicted word reading accuracy in EFL, and dyslexia, years of studying EFL privately, and NL RAN predicted EFL word reading fluency. Dyslexia and NL phoneme blending predicted the accuracy, and NL RAN--the fluency of EFL nonword decoding. These findings confirm that difficulties in FL acquisition result from NL phonological processing deficits, characteristic of dyslexia. Our results also showed relationships between NL phonological processing and EFL reading that were analogical to the ones observed for NL. The pattern of relations between NL phonological processing, NL reading, and EFL reading was similar for reading fluency, but not for reading accuracy in the compared groups. Both NL phonological processing and NL reading facilitated EFL reading, though it was more conspicuous in the control group, which suggests that readers with dyslexia benefit less from their NL reading skills when learning to read in FL.