This presentation gives a short overview of the characteristic properties of porous metals manufactured by powder metallurgy based space-holder methods. In this family of methods, a metal powder is first mixed with a filler material in the powder form. The mixture is then compacted and subsequently sintered to form a metal network. The filler material is removed either before, or during, or after the sintering to generate the pores in the resultant porous metal. The as-produced porous metals have distinctive porous structures. In effect, the pores are negative replicas of the particles of the filler material and the porosity is determined by the volume fraction of the filler material in the powder mixture preform. Pore shape, pore size and porosity can all be controlled accurately. The functionality of the porous metals derives from the combinations of distinctive characteristics of the solid and gaseous phases. The solid phase provides geometrical architecture, strength, electrical conductivity, thermal conductivity, magnetic shielding, acoustic barrier etc,, while the gaseous phase offers compressibility and allows fluids to flow through. This presentation focuses on recent developments in the manufacture of hierarchical porous structures composed of micro- and nano-scale pores by combining a space-holder method and a dealloying process.