Results of first-principles calculations of the band structure of Na xCoO2 (x=0.33 and 0.61) are presented. In Na 0.33CoO2, charge ordering of Co3+-Co 4+ ions has been obtained. Ferromagnetic and antiferromagnetic orderings have been considered. Magnitudes of trigonal splitting of the t 2g band of Co and intersite hopping integrals have been determined in the basis of Wannier functions. Magnitudes of the parameter of exchange interaction have been calculated in terms of the Heisenberg model.