This paper presents our preliminary results for a three-dimensional (3D) imaging of an on-the-move target using a MIMO millimeter-wave (mm-wave) radar, which uses 9 transmitters and 12 receivers. The operating frequency of the mm-wave radar is from 70 GHz to 77 GHz. Experimental results show that the images can be created as the target under detection moves in front of the radar system, which is combined with 3D video to show the continuous movement of the target. This preliminary work paves the way towards a mm-wave imaging system that can be used at checkpoints; thus enabling on-the-move detection of potential threats, enhancing passenger's overall experience, and achieving a high scanning throughput.