This paper studies the theoretical relationships between core research lines of sociology, such as intergenerational mobility, class structure and cultural capital, with educational mismatches. By educational mismatch we mean two things. Firstly, an individual can be horizontally mismatched whereby their field of study is inadequate for the job.Another direction of educational mismatch is the so called vertical mismatch, where the worker possesses more/less education than the job requires resulting in over-/under-education. While analyzing the educational mismatches we keep present the conclusions of Rational Action Theory on individuals’ rational choices in their educational careers.We arrive to conclusions where the influences between educational mismatches and social classes are bidirectional and one can establish fairly clear theoretical links between class of origins and likelihood of being educationally mismatched.