The structure and magnetic properties of thin polycrystalline films of Co100 – xWx (0 ≤ x ≤ 30) deposited by magnetron sputtering on glass substrates are investigated including those containing buffer layers of Ta, W, and Ru. It is found that films of pure Co are non-single-phase and contain hcp and fcc crystalline modifications. Doping leads to an increase in the concentration of the fcc phase and an enhancement of the texture of the (111) type, and subsequently to the amorphization of the films. The buffer layers influence to a certain extent on the depth and concentration localization of these transformations. A characteristic feature of the magnetism of Co–W films is a significant perpendicular component in the macroscopic magnetic anisotropy, which leads to a “supercritical” magnetic state. It is shown that its source is the textured fcc phase, the crystalline anisotropy of which is enhanced as a result of doping of cobalt with tungsten.