In this paper the superconducting properties in La 1.85S Sr 0.15 Cu 1-x Mn x O 4 and La 1.85-2x Sr 0.15+2x Cu 1-x Mn x O 4 samples are discussed. The superconducting transition temperature keeps constantly at 37 K for all superconducting samples. The suppression of superconductivity in these systems does not fit the Arbrikosov and Gork'ov theory which predicts that Tc should decrease in the presence of magnetic impurities in the lattice. The magnetic pair-breaking effect is not the reason for the suppression of superconductivity in Mn doping systems. The localization of carriers in the CuO 2 plane induced by Mn doping should be responsible for the suppression of superconductivity.