Potential energy surfaces and fission barriers of superheavy nuclei are analyzed in the macroscopic-microscopic model. The Lublin-Strasbourg Drop (LSD) is used to obtain the macroscopic part of the energy, whereas the shell and pairing energy corrections are evaluated using the Yukawa-folded potential. A standard flooding technique has been used to determine the barrier heights. It was shown the Fourier shape parametrization containing only three deformation parameters reproduces well the nuclear shapes of nuclei on their way to fission. In addition, the non-axial degree of freedom is taken into account to describe better the form of nuclei around the ground state and in the saddles region. Apart from the symmetric fission valley, a new very asymmetric fission mode is predicted in most superheavy nuclei. The fission fragment mass distributions of considered nuclei are obtained by solving the 3D Langevin equations.