The study of dynamical properties of crystals near structural phase transitions is a very challenging subject. The dynamics may have various origins of intrinsic (moving phase transition clusters, domain walls, molecular reorientations, glass freezing, …) or extrinsic (impurities, dislocations,…) nature. Some of these processes lead to a poly-dispersive behaviour of macroscopic susceptibilities. Frequently the obtained data are fitted by empirical functions, e.g. Cole-Cole-, Cole-Davidson-, Havriliak-Negami-, etc. functions, thus leaving the origin for the observed relaxation unclear. We present two examples of non-exponential relaxations whose origins can be described by simple models: The influence of order parameter fluctuations to the elastic susceptibility yielding a dispersion which resembles a Cole-Davidson-type behaviour and the influence of heat diffusion to macroscopic susceptibilities near phase transitions, respectively.