In recent years, there have been concerns in the UK regarding the uptake of particular subjects in post-compulsory education. Whilst entries for Advanced level (A-level) subjects such as media studies have experienced considerable growth, entries for A-level physics have, until recently, been declining, prompting fears of a skills crisis in future generations. This study applied an established psychological theory, the theory of planned behaviour, to explore the drivers behind students' subject choice at A-level, specifically focusing on students' intentions to study physics and media studies. Multiple regression analyses supported the predictive validity of the theory in this context, with the three predictor variables (attitude, subjective norm and perceived behavioural control) accounting for 66% of the variance in students' intentions to study physics and 68% of the variance in students' intentions to study media studies. Furthermore, for both subjects, attitude and subjective norm were found to be significant predictors of intentions. Hence, students with higher intentions to study physics or media studies exhibited a more positive attitude towards choosing this subject and perceived greater social pressure from significant others. Analysis of the beliefs underlying students' subject choices suggested that the influence of parents was particularly important to students, as were beliefs about the positive outcomes of choosing physics or media studies in terms of student's future career and education prospects. This suggests that initiatives aimed at increasing the uptake of subjects such as physics in the future might be best targeted in these areas.