We report on the crystal structure of epitaxial ZnSnN2 films synthesized via plasma-assisted vapor deposition on (111) yttria stabilized zirconia (YSZ) and (001) lithium gallate (LiGaO2) substrates. X-ray diffraction measurements performed on ZnSnN2 films deposited on LiGaO2 substrates show evidence of single-crystal, phase-pure orthorhombic structure in the Pn2(1)a symmetry [space group (33)], with lattice parameters in good agreement with theoretically predicted values. This Pn2(1)a symmetry is imposed on the ZnSnN2 films by the LiGaO2 substrate, which also has orthorhombic symmetry. A structural change from the wurtzite phase to the orthorhombic phase in films grown at high substrate temperatures similar to 550 degrees C and low values of nitrogen flux similar to 10(-5) Torr is observed in ZnSnN2 films deposited on YSZ characterized by lattice contraction in the basal plane and a 5.7% expansion of the out-of-plane lattice parameter. (C) 2016 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).