The invention relates to a radial fan (1), preferably a high-speed radial fan, comprising a blower wheel (8), a housing (2) which receives a rotor (6) and a stator (5) of an electrical drive (4) of the blower wheel shaft (7), and a cooling system. The aim of the invention is to develop one such radial fan in terms of the cooling system required. To this end, paths (30, 37) for a first cooling medium (Ki) and a second cooling medium (K2) are provided in the housing (2), the second cooling medium (K2) being cooled by the first cooling medium (Ki) by means of the housing (2), and said paths (30,37) are separated from each other by intact material walls (40) of the housing (2).