My talk will be focused on a class of objects known as X-ray binary stars. In the introduction, I will describe what an X-ray binary is, what their types are, what physical processes take place in them and what observational features they lead to. Then I will briefly remind you about the basics of polarization — where does it come from and how, and most importantly, why it should be measured in X-ray binaries. The main part of the talk will be based on the results of my doctoral studies. In particular, I will discuss the models for orbitally variable optical and X-ray polarization that we have developed in our Turku HEA group and show what constraints on the physical parameters of such systems we can impose with them.