The effective thermal conductivity of a powdery material, comprising heal conduction in the solid particles and in gas and temperature radiation across the pores, was determined by the transient hot wire method. The materials investigated were LaNi4.7Al4.7Hx, which is practically applied at medium temperature, and HWT 5800, applied at low temperatures. The temperature range investigated was -80 to +140 degrees C, the pressure range 10(-6) to 60 bar. The porosity of the powder material in the state of delivery was 0.045 and 0.531. Concentratiop/pressure isotherms (CPI) and the effective thermal conductivity k(eff) were measured. Various filling gases (H-2, He, N-2, Ar) were used. There is a clear effect of the gas in the slate of delivery of the powder. An effect of particle decay can be observed. The effective thermal conductivity depends primarily on the hydrogen pressure, while the temperature has only an indirect influence.