A tangential X-ray pinhole camera based on a gas electron multiplier (GEM) detector was installed on KSTAR to study high temperature plasmas emitting X-ray photons in the energy band of 4-15 keV. The camera system consists of a triple-GEM gas chamber with a readout printed circuit board and a pinhole to image the plasma in two dimensions (2-D). The advantages of this tangential camera system include its compactness, high efficiency, energy discrimination in bands, and selectivity of the photon energy range etc. This camera system allows a selection of the viewing area through a remote control of the entire setup. The Philips-Tikhonov algorithm for tangential reconstruction was used to visualize the poloidal cross-sectional images. Phantom tests were performed with synthetic D-shaped plasma images and a comparison with the magnetic equilibrium flux surfaces from the real-time EFIT code obtaining a good agreement between each other. The 2-D X-ray images of the KSTAR plasma were successfully acquired during sawtooth crash, electron cyclotron heating, vertical displacement event, and emissivity from the injected trace Ar impurity. (C) 2016 Elsevier B.V. All rights reserved.