The thermal conductivity of Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) layers, as well as the thermal boundary resistance at the interface between the GST and amorphous SiO{sub 2}, were measured using a PhotoThermal Radiometry experiment. The two phase-changes of the Ge{sub 2}Sb{sub 2}Te{sub 5} were retrieved, starting from the amorphous and sweeping to the fcc crystalline state at 130 {sup 0}C and then to the hcp crystalline state at 310 {sup 0}C. The thermal conductivity resulted to be constant in the amorphous phase, whereas it evolved between the two crystalline states. The thermal boundary resistance at the GST-SiO{sub 2} interface was estimated to be higher for the hcp phase than for the amorphous and fcc ones.