The 3D fatigue crack growth behaviour in 3PB-specimens or in cantilever beam specimens under respectively bending or torsion loading, with inclined planes for the initial crack, is investigated by the Dual Boundary Element Method (DBEM). Mixed mode conditions along the crack edge are characterized: Stress Intensity Factors (SIFs) are determined using the J-Integral method, and the crack growth direction is computed by the minimum strain energy density criterion. The evolving crack shape (spatially twisted or twisted and warped crack faces), computed by the DBEM model, is successfully compared with experimental findings and FEM results