CASSCF and CASPT2 calculations have been performed on the ground and two lowest singlet and triplet excited states of the protonated dihydrate. Two subsystems can be identified in the excited states : an excited water molecule and a ground state oxonium ion. The electric properties have been computed (dipole moment and dipole polarizabilities). The dipole polarizabilities are very large in the excited states of the complex (up to 500 au for the largest component). This can be due to the presence of nearly degenerate higher excited states or to an easy proton/hydrogen transfer process. The excitation energies, around 8 eV for both states, show that the photodissociation of H5O2+ is probably possible in the atmosphere, The stabilization energy of the excited states with respect to the isolated subsystems is about 5-6 kcal/mol, including the relaxation contribution.