In this study the effects of various anions (SO4 2-, ClO4and PO4 3-) were investigated on the hydrothermal treatment of WO3 from Na2WO4 and HCl at 180 and 200 °C. The products were analyzed by XRD and SEM. With the usage of SO4 2the obtained product was hexagonal (h-) WO3 in the form of nanorods at both temperatures. Applying ClO4resulted in a mixture of WO3•0.33 H2O and small amount of m-WO3 at 180 °C and pure WO3•0.33 H2O at 200 °C. The morphology was consisted of cuboid shapes arranged into spherical structures at 180 °C and longitudinal ones at 200 °C. By the application of PO4 3no product formed at either temperature. Using the combination of SO4 2-, and ClO4the product was h-WO3 at both 180 and 200 °C with rod-like crystals; thus, the effect of ClO4was overdominated by the SO4 2ions. Utilization of PO4 3together with SO4 2-, and/or ClO4resulted again in no product, meaning that adding PO43to the reaction mixture completely blocks the hydrothermal formation of solid products by forming water soluble phosphotungstic acids.