The precise theoretical description of the potential energy surface is
required for the proper explanation of spontaneous fission of heavy 
nuclei.
The HFB theory with the D1S Gogny force has been successfully used to
determine fission barriers. The calculations has been performed in the
multidimensional space of deformations.

The potential energy surface of the 252Cf will be presented as an example 
of nuclei with mass A~250. The bimodal fission of 258Fm will be explained. 

The HFB theory has been also applied to predict fission and alpha-decay 
half-lives of super-heavy nuclei.