Abstract: Cosmological constraints on the sum of the neutrino masses can be relaxed if the number density of active neutrinos is reduced compared to the standard scenario, while at the same time keeping the effective number of neutrino species Neff ≈ 3 by introducing a new component of dark radiation. In this talk I will discuss a simple complete model to realise this idea, which simultaneously provides neutrino masses via the seesaw mechanism.