  We investigate the evolution of a disk wind into a collimated jet under the
influence of magnetic diffusivity. Using the ZEUS-3D code in the axisymmetry
option we solve the time-dependent resistive MHD equations for a model setup of
a central star surrounded by an accretion disk. The disk is taken as a
time-independent boundary condition for the mass flow rate and the magnetic
flux distribution. We find that the diffusive jets propagate slower into the
ambient medium, most probably due to the lower mass flow rate in axial
direction. Close to the star we find that a quasi stationary state evolves
after several hundreds (weak diffusion) or thousands (strong diffusion) of disk
rotations. Magnetic diffusivity affects the protostellar jet structure
de-collimating it. We explain these effects in the framework of the Lorentz
force.
