Two different types of inhomogeneity of optical thin films resulting from the deposition conditions are considered to be the origin of volume scattering. With the use of a theory based on a first-order Born approximation, both structure types can be treated easily. In the case of an oblique columnar structure, the light-scattering patterns show a pronounced anisotropy and a strong dependence on the side at which the light enters the sample. As explanation of these facts, the role of the four partial scattering processes inside the film is revealed, leading to a simple diffraction model that reproduces the main scatter features and makes the individual physical processes involved more obvious. Inclusions without any preferred orientation only contribute to other isotropic background scatter sources such as roughness, allowing the use of anisotropic scatter for investigations of structure. structure, oblique deposition, anisotropy, granular structure.