Context. The Cassini mission in the Saturnian system is an outstanding opportunity to improve our knowledge of the satellites of Saturn. The data obtained thanks to this mission must be balanced with theoretical models. Aims. This paper aims at modelling the rotation of Mimas with respect to its possible internal structure. Methods. We first built different interior models, considering Mimas to be composed of two rigid layers with different porosity. Then we simulated the rotational behaviour of these models in a three-degree of freedom numerical code, considering the complete ephemerides of a Mimas whose rotation is disturbed by Saturn. We also estimated the deviation of its longitudinal orientation caused by tides. Results. We expect a signature of the internal structure up to 0.53° in the longitudinal librations and an obliquity between 2 and 3 arcmin, the exact values depend on the interior. Conclusions. The longitudinal librations should be detectable, but inverting them to arrive at clues on the internal structure of Mimas is challenging.