High-resolution X-ray diffraction has been used for the structural characterization of thin single porous silicon (PS) layers and superlattices. Thin PS layers, in the range of 100-1000 nm, exhibit several thickness interfringes, giving evidence for the lateral homogeneity of the layer thickness. For PS superlattices, several satellite reflections are visible in the diffraction pattern. The analysis of these experimental results using simulations allows us to deduce structural information of this new kind of silicon heterostructure.