Between 70 and 500 GHz a number of transitions of (SeO2)-Se-76, (SeO2)-Se-77, (SeO2)-Se-78, (SeO2)-Se-80, and (SeO2)-Se-82 in the ground and excited v(2)=1 vibrational states have been measured. Transitions of (SeO2)-Se-80 in the excited nu(2)=2 State and of (SeO2)-Se-74 in the ground state have been measured as well. Greatly improved sets of the parameters of A-reduced Watson's Hamiltonian have been obtained in the I-r representation.