Germanium has been under the spotlight of researchers for several decades and it has been studied both from the theoretical and experimental point of view. Its characteristic conduction band, with four minima at the edges of the Brillouin zone, is a playground for material scientists.Here we present the magnetic resonance of conduction electrons in bulk Ge crystal and in Ge quantum wells (QWs). The carriers were generated in the bulk by illumination, while they were introduced in the QWs by modulation doping. In the bulk, we observed ESR lines with axial symmetry and principal g values gp= 1.920 and gt= 0.839, as expected for electrons in conduction band-like states. In the QWs there is a dependency on the thickness of the well, in agreement with the model proposed by Baron et al.[1]. Relaxation times have been estimated by the saturation curves and linewidth, providing exceptionally long values with respect to the bulk.