The modelling of scattering problems by targets of arbitrary shape placed in possibly complex environments is in many cases a challenging task. However, the availability of accurate and reliable forward-scattering techniques is of fundamental importance both for propagation prediction and for providing benchmarks for novel inversion algorithms and imaging techniques, as well as for better understanding the measured data. Possible fields of applications include remote sensing of buried objects or detection and localization of targets behind walls. Beyond the radar applications, a significant interest has been recently devoted to the propagation modelling at high frequencies in a building’s interior with UWB sources, including the scattering of common objects in an indoor environment. Possible approaches may include numerical full-wave techniques, also optimized from the point of view of computational times and memory requirements. High frequency asymptotic techniques are also of interest for addressing the computational issues relevant to very large environments. Analytical methods may be considered, too, when target geometry can be described through canonical shapes. In all cases, shadowing effects, attenuation, multipath propagation, refraction, and diffraction need to be considered for an accurate modelling, especially when dealing with complex scenarios.