In our research we addressed the question what the relationship is between phonological short-term and working memory capacity and performance in an end-of-year reading, writing, listening, speaking and use of English test. The participants of our study were 121 secondary school students aged 15–16 in the first intensive language training year of a bilingual education program in Hungary. The participants performed a non-word repetition test and took a Cambridge First Certificate Exam. Fifty students were also tested with a backward digit span test, measuring their working memory capacity. Our study indicates that phonological short-term memory capacity plays a different role in the case of beginners and pre-intermediate students in intensive language learning. The backward digit span test correlated very highly with the overall English language competence, as well as with reading, listening, speaking and use of English (vocabulary and grammar) test scores.