The NMR pulsed gradient spin echo (PGSE) self-diffusion technique is applied to a system with permeable barriers. The system is a highly concentrated emulsion consisting of 97% water, and its internal structure is one of closely packed water droplets which are separated by thin oil films. These oil films are permeable to water, and the emulsion can therefore be considered as belonging to the general class of porous systems. Recently, Callaghan and co-workers showed both theoretically and experimentally that under certain conditions one may actually detect diffraction-like effects when the ROSE experiment is applied to porous systems. We report here for the first time such diffraction-like effects in an emulsion system, which were observed when examining the water diffusion in the emulsion system mentioned above with the PGSE experiment. From the experiment the mean droplet size may be determined.