Two technologically important materials - cadmium tungstate CdWO4 and zinc tungstate ZnWO4 - are studied in details using the plane wave based first-principles calculations. The optimized crystal structures were used to calculate the electronic and optical properties of both materials. Comparison of the calculated results with the available in the literature experimental X-ray photoelectron spectra (XPS) and reflectivity spectra yielded good agreement and allowed for assignment of the experimentally observed features, including those induced by difference between the Cd 4d and Zn 3d states. In addition, the variations in the electron density distributions related to two crystallographically in equivalent oxygen positions were revealed. (c) 2012 Elsevier B.V. All rights reserved.