Learners’ language background is one of the factors which may influence the amount and functions of own-language use in English instruction. This article reports a study in which a group of almost 400 Polish and Norwegian secondary school learners of English were asked how their own languages are used in the classroom, how they use them when they study English at home, and, finally, how they assess their usefulness in relation to various aspects of learning English. In the study, learners’ behaviour and beliefs were investigated through a questionnaire and through interviews. The results indicate that Polish and Norwegian secondary classrooms are in many respects similar concerning how the students’ own languages are used. Also, there were few significant differences between Polish and Norwegian students’ attitudes to whether own-language use is useful for learning English. More significant differences were found in how these two groups of learners use their own languages to support the learning of English at home.