This study investigates differences and similarities in the the production of errors influenced by the mother tongue in the written performance by twelve-year-old Polish, Italian and Hungarian students of English as a second language. The essays produced by the students were analysed and syntactic, vocabulary and pronounciation errors were identified and classified. Results revealed that most students often rely on their first languages and Hungarian students commit more errors than the Polish or Italian students. The results also suggest that transfer is an important source of errors in Polish, Italian and Hungarian students’ written compositions.