The effects of hydrogen diffusion on p-n GaAs junctions have been studied by electron beam induced current (EBIC) and cathodoluminescence (CL) at room temperature. Hydrogen passivates both the acceptors in the p-side of the junction and the donors in the n-side of the junction. As a consequence the diffusion lengths increase, the surface recombination velocities decrease, and, finally, the CL intensity increases after the hydrogen treatment. The observation of hydrogen effects on both sides of the junction indicates that hydrogen diffuses at least in the neutral charge state. We also observe an electron-beam induced reactivation of the passivated centers after exposition of the sample for some minutes to the electron-beam.