This paper presents experimental results obtained for innovative thin (2 mm) copper-water and copper-acetone heat pipe (HP) plates recently developed at Thermacore. The heat pipe plates are about 120 mm wide and 250 mm long and are developed mainly for electronics cooling applications. There are multiple interconnected fluid channels in the plate, partially filled with liquid. These channels act as miniature heat pipes effectively spreading thermal energy from a heat source, attached to the plate, to the plate surfaces exposed to free-convection air cooling. Inner surfaces of the fluid channels are partially covered with a capillary structure to enhance heat transfer and liquid return during the two-phase fluid circulation with evaporation and condensation inside the channels.