One of the most fundamental innovations in higher education is the introduction of the method known as problem-based learning (PBL). While literature has largely focused on its learning goals and the transition from lectures to tutorials, little research has problematised why this is a successful methodology and what we consider as students' success. Drawing upon various ethnographic techniques, the authors analyse PBL as a field of expectations in light of Expectation-Value Theory. Beyond merely showing that PBL is a culturally constructed practice, the article elaborates on how students' expectations inform practices, performance and evaluation, which is important for assessing the successfulness of the method. By discussing students' expectations, dynamics and power relations, the present article is a contribution to the research addressing what has come to be known as the 'black box' of PBL.