In the present work we review some X-ray and neutron based techniques capable of measuring diffusion lengths in thin films with an accuracy of a fraction of a nanometer. The techniques have been used for studying both self-diffusion of the constituent species in a thin film, as well as interdiffusion at the interfaces in multilayers. The high accuracy of the techniques in depth pro. ling of an element or a specific isotope makes very low diffusivities similar to 10 (23) m(2)/s, amenable to measurements, and allows one to study the subtle effects of factors like internal stresses or structural relaxation on self-diffusion in compositionally homogeneous films. Depth selectivity of X-ray standing wave technique in multilayers makes it possible to distinguish between diffusion at the two types of the interfaces, namely A-on-B and B-on-A, in a single multilayer structure. (C) 2009 Elsevier B.V. All rights reserved.