The present invention relates to a method for non-destructive, contact or non-contact inspection of composite assemblies using radiation having a frequency in the terahertz range (10 GHz-10 THz) of the spectrum, whereby said method is implemented as an embodiment of the system for non-destructive, contact or non-contact inspection of composite assemblies using terahertz radiation, that is also claimed under the present invention. Said method enables the forming of a two or three-dimensional image of the material structure of an assembly of composite materials, from which image detection and analysis of material conditions of the composite materials forming said composite assemblies is possible, irrespective of the way that the composite materials forming said composite assemblies were joined together, and without the need for a priori knowledge about the structural characteristics, shape or configuration of said composite materials (for instance layered, foam, placed on metal substrate).