We study theoretically the spin-dependent electron-electron scattering in ordered and disordered magnetic surfaces. With the aid of the screened Korringa-Kohn-Rostocker (KKR) method and the density functional theory within the local-density approximation we calculate the spin-dependent Kohn-Sham crystal potential in which two excited electrons are propagating. The electronic band structure is also calculated and it is shown that a coincident measurement of two excited electrons from a magnetic surface gives access to the spin-resolved spectral distribution of the band electrons. We also discuss the case of disordered metals and point out the conditions under which the electronic spectral properties of the surface can be imaged by means of coincident electron measurements.