The quaternary transition metal oxyselenide La2O2ZnSe2 has been shown to adopt a ZrCuSiAs-related structure with Zn2+ cations in a new ordered arrangement within the [ZnSe2](2-) layers. This cation-ordered structure can be derived and described using the symmetry-adapted distortion mode approach. La2O2ZnSe2 is an direct gap semiconductor with an experimental optical band gap of 3.4(2) eV, consistent with electronic structure calculations.