My research deals with both the perception and production of L2 consonants. The aim of this research is to find whether the interference of the L1 sound system on L2 segments takes place at the phonological or phonetic level. In order to study this issue, I am analysing the acquisition of English consonants by speakers of two Catalan dialects with subtle differences in their phonological systems. In this talk I will present the results of the perception study I have carried out and what they suggest for the competing hypotheses.