An system for detecting contraband, particularly explosives or other energetic materials. The system includes a source of ionizing radiation that irradiates an item under inspection. The radiation stimulates the emission of RF energy from objects within the item under inspection. The characteristics of the emitted RF energy reveals information about the material composition of the objects. The system detects this emitted RF energy and comparers it to a signature of RF emissions from contraband objects. Apparatus to detect and analyze RF emissions may be constructed as a stand-alone unit or may be incorporated into an imaging system in which the ionizing radiation is used to form an image of the item under inspection. Similarly, the RF analysis may be used, in the first instance, to determine whether an object contains a contraband item or may be used as a second level analysis to clear alarms generated by analysis of images formed by the imaging system.