Structure studies based on either the Strutinsky method or self-consistent Hartree-Fock (HF) and Hartree-Fock-Bogoliubov (HFB) mean field theories suggest that superdeformed (SD) states might well develop at large quadrupole deformation (i.e. βgt-or-equal, slanted0.5) in mercury isotopes. In this work, we predict the existence of Iπ=0+ shape isomers which might take place at excitation energies of 4.4, 5.4 and 6.9 MeV in 190Hg, 192Hg and 194Hg, respectively. These SD levels are obtained by solving the Griffin-Hill-Wheeler equation in the gaussian overlap approximation. Inputs for that collective hamiltonian are tensors of inertia as well as potential energy surfaces which are deduced from constrained HFB calculations based on the finite-range, density-dependent effective force of Gogny.