Excitation energies and electromagnetic transition strengths in even-even ^96-108Mo nuclei have been described systematically by using the proton-neutron interacting boson model (IBM-2). It appears that the properties of low-lying levels in these isotopes, for which the comparison between experiment and theory is possible, can be satisfactorily described by the IBM-2 model, provided proper account is taken of the presence at low energy of states having a mixed-symmetry character. It seems possible to identify, in each isotope, a few states having such a character, the lowest ones being either 2₂⁺ or 2₃⁺ levels. It is found that these nuclei are in the transition from U(5) to SU(3).