ABSTRACT This study examines the attitudes of CLIL learners to both language and subject learning in the context of Madrid’s Spanish-English Bilingual Education Program. The research compared 70 students enrolled in two secondary school strands with differing CLIL exposure (high versus low) in terms of their attitudes towards the languages of instruction and their beliefs about how content subjects are taught in the L1 (Spanish) and the L2 (English). Their answers to two open-ended questions from a longer questionnaire were coded using thematic analysis. The results indicate that, whilst participation in either the high- or the low-exposure strand has an effect on students’ preferences regarding the language of instruction, it does not seem to influence their orientation towards the practical value of CLIL. In addition, students tend to attribute similarities and differences in the teaching of subjects in the L1 and the L2 to the content and to the change in language of instruction. These results are further discussed by addressing the amount of CLIL instruction across strands and by contextualising this approach in a primarily monolingual context and mindset, where certain expectations clash with fears and presuppositions concerning the effect on L1 literacy of learning in an additional language.