We investigated the effect of doping on the crystallographic, dynamic and magnetic properties of (Cul _ zZnz)GeO3 as well as Cu(Gel _xmx)O3 with A = A1, Si, Ga, As, In, Sn, Sb and Ti. A large solubility was only observed for Zn, Si and Ti. For those elements, the lattice parameters show a linear dependence on doping within the whole solubility range. The spin-Peierls transition temperature Tsp decreases linearly with doping, though the slope is strongly dependent on the dopant. For Zn-doping, a N6el-like ground state which exhibits spin-flop behavior appears for higher doping after the complete disappearance of the spin-Peierls ground state. Si-and Ti-doped samples exhibit a similar phase in a coexistence with the spin-Peierls ground state. The analysis of the susceptibility in the spin-Peierls phase for low Zn content indicates a reduction of the dimerization within the Cu chains and the energy gap upon doping. Whereas for Si and Ti all phonon frequencies changed linearly with the doping level, we observed in Zn-doped samples for some phonons a clear minimum at the composition z = 0.02 where the spin-Peierls transition disappears, suggesting a strong spin-phonon coupling for these modes. For higher Zn concentrations, no lattice dimerization can be observed by Raman scattering.