Planck satellite provides for the first time the possibility to detect galaxy clusters using their Sunyaev-Zeldovich (SZ) effect signature covering the full sky (Planck Col XXIX, 2013). Planck SZ catalogs I and II include more than 1900 sources, of which 700 remain unknown. The study of the purity of these samples and the characterization of SZ sources is essential to perform cosmology with cluster counts. With this aim in mind, the IAC-Planck group is performing the optical validation and characterization of these samples through two long-term observing programs at Canary Island observatories, the ITP 13B15A and the large-term 15B-17A. In this talk we will present intermediate results of this validation program. Using photometric and spectroscopic information (mainly multi-object techniques) we estimate redshifts and dynamical masses in order to minimize the errors in the Msz-Mdyn scaling relation and the SZ clusters mass function which allow a better determination of cosmological parameters (mainly Omega_m, sigma_8 and neutrino mass) from Planck SZ survey.