The influence of the shape of magnetic particles and dielectric permittivity of the medium is investigated on the magneto-optical properties of the nano-dispersive structures using the thin discontinuous Co films. The behaviour of the magneto-optical spectra of thin Co films was explained in the framework of the effective medium approximation. The results have confirmed the significant change of the components of the tensor of effective dielectric permittivity and subsequently of the magneto-optical and optical properties which brought about the change of the shape of magnetic particles. These calculations proved that a good agreement between the experimental results and the theoretical calculations is achieved if the shape of the particles is taken into account