In the sociology of education, the rational choice paradigm may be considered the dominant model used to explain educational choices and inequalities in education. The two main versions of this theoretical perspective come from the field of psychology (the theory of planned behaviour) and the field of sociology (rational choice theory). Both theories congruently hold that educational choices and inequalities in education are the result of instrumentally rational choices that take different levels of resource scarcity into account. Apart from this consensus, the two versions of the theory differ in their theoretical determination of the explanatory factors deemed relevant and in the level of rationality attributed to the actors. A growing number of empirical studies explore the empirical adequacy of the assumptions drawn by each of these two theoretical versions and check the validity of the resulting prognoses. This chapter compares the basic assumptions drawn by the theoretical versions of the rational choice paradigm and presents an overview of the current state of the empirical examination. The results show that both the theory of planned behaviour and rational choice theory cover important aspects of educational choices and can explain a relevant part of the effects of social origin. Empirical evidence, however, reveals certain limitations of these two versions of rational choice theory. Possible solutions to this problem are discussed in the conclusions at the end of this contribution.