Single crystals of CeAsSe were synthesized by a reaction of the elements using iodine as a mineralization agent at 900 degrees C. The crystal structure was established from single crystal X-ray diffraction data and obtained from a pseudomerohedrically twinned specimen (space group Pnma, a = 5.7969(1) angstrom, b = 5.7664(1) angstrom, and c = 17.8196(6) angstrom; Z = 8). CeAsSe crystallizes in the GdPS type of structure and contains infinite cis-trans chains of arsenic atoms, packed between two-dimensional slabs of alternating Ce and Se atoms. The chemical composition of the investigated crystals was determined to be CeAs1.01(1)Se0.99(3). High-resolution diffraction experiments with synchrotron radiation clearly evidence the orthorhombic metric. However, variations in composition or temperature profile in the synthesis procedure lead to vanishing distortion, that is, disappearance of reflection splitting and superstructure reflections, and thus to a tetragonal metric within the resolution of the synchrotron-based diffraction experiments. CeAsSe can be expressed as consisting of Ce3+, As1-, and Se2- as an electronic precise Zintl-type compound. This interpretation is consistent with the results of X-ray absorption spectroscopy at the Ce-L-III edge and magnetic susceptibility data. The temperature dependence of a semiconductor was observed in electrical resistivity measurements.