In this talk, we will present a semi-classical approach of quantum limits for a sub-Laplacian on a step 2 nilmanifold. These manifolds are obtained by (left)-quotienting a nilpotent Lie group by one of its co-compact sub-groups. They present a rich geometry ; for example, they can enjoy a contact or a quasi-contact structure. We will consider sequences of eigenfunctions of a sub-Laplacian defined on this manifold and we will describe some results about the structure of the weak limits of densities associated with these sequences. These results have been obtained in collaboration with Véronique Fischer and Steven Flynn (University of Bath).