Disclosed herein is a method and system for detecting potentially hazardous and/or explosive material concealed under clothing or in luggage. Through the emission, reflection, and reception of microwave radiation, a 3D image of a targeted area can be constructed. The image will show the outline of a moving person as well as any dielectric objects potentially hidden on their body. By measuring phases and amplitudes of microwaves reflected off a dielectric object, the optical path of the microwave through a hidden object can be determined, thus allowing for the creation of a 3D microwave image of a targeted area. Several emitters and receivers can be utilized at once, and video imaging can also be superimposed over the microwave image for improved detection accuracy. The invention has security and safety applications across the nation, particularly in areas of mass transit and large public events.