[en] We investigated the dielectric properties of pure and lanthanum modified bismuth titanate thin films obtained by the polymeric precursor method. X-ray diffraction of the film annealed at 300 deg. C for 2 h indicates a disordered structure. Lanthanum addition increases gradually the dielectric permittivity of films, keeping unchanged their loss tangent. From C-V curve we can see no hysteresis behavior indicating the absence of domain structure. The decrease in the conductivity for the heavily doped Bi₄Ti₃O₁₂ (BIT) must be associated to the unidentified crystal defects. For comparison, dielectric properties of crystalline BIT film were also investigated