Recently, Gamal et al. [Chin. Phys. Lett. 22 (2005) 1530] reported the results of electrical conductivity, Hall effect and thermoelectric measurements on p-type Tl2S5 single crystals. From the experimental data for the temperature dependence of differential thermoelectric power, Gamal et al. determined the values of 2.66 X 10(-41) kg and 2.50 x 10(-41) kg, respectively, for the effective masses of electrons and holes in p-type Tl2S5, which are about ten orders of magnitude smaller than the free election mass (9.11 x 10(-31) kg). We argue that the anomalously small values obtained for the effective mass of charge carriers in Tl2S5 have no physical significance.