Magnetic properties of melt-processed YBCO doped with different content of Li, Ni and Pd impurities are reported. The increase of critical currents of doped materials has been observed in intermediate magnetic fields. The normalized pinning force is scaled into a single curve for all measured isotherms (60–77 K) for the samples with higher impurities level. The analysis of magnetic relaxation measurements at a field of 1 T and in the temperature interval between 10 and 70 K reveals a logarithmic dependence of the effective activation energy vs. current density. The observed time dependence of the magnetization in doped materials can be described in the framework of collective pinning theory.