Due to spectral instability the eigenvalues of non-self-adjoint differential operators are often highly unstable under small perturbations. There are now several results stating that when we add a small random perturbation, we get Weyl asymptotic distribution of eigenvalues, with probability close to 1 in the semi-classical limit, and almost surely in the limit of large eigenvalues. Moreover the bounds on the resolvent tend to improve under the action of such perturbations. We describe some of these results, due to M. Hager, W. Bordeaux-Montrieux, and the speaker, as well some underlying ideas and proofs.