By means of r.f. sputtering of the ceramic targets or pressed powder targets with the chemical constitution of Pb (Zr0.52Ti0.46W0.01Cd0.01) O3the polycrystalline thin ferroelectric films with the perovskite type structure and of thicknessdf= (1–2, 5) × 10−6m on metal (stainless steel, platinum) or ceramic (polycor) substrates have been obtained. In case of thin film deposition on steel substrate and on platinum at low temperatures (Tx< 723 K) the nonferroelectric intermediate layer with the same chemical constitution but with the pyrochlore type structure have been created. Results of the X-ray analysis and dielectric investigations (low frequency dispersion) have proved existence of such a structure. The structural phase transition (P4mm Pm3m) takes place in the thin ferroelectric films. This is a diffuse type transition and the degree of diffuseness depends on the structural perfection of the thin films. The measure of the structural perfection of the thin films was taken to be the mean value of the lattice strains (microdeformations) ⟨ Δd/d⟩ where “d”-interplane distance and the mean dimension (D) of the areas of coherent X-rays scattering (crystallites). With increase in ⟨ Δd/d⟩ and decrease inDthe degree of diffuseness increases. For quantitative and qualitative describing of this dependence in thin PZT films the phenomenological model of diffused phase transition developed earlier by the authors for thin BaTiO3films has been applied. In this case a good agreement between theory and experiment have been achieved for low values of ⟨ Δd/d⟩.