Herein we report on the results of our investigations of the phase formation in the aqueous uranyl-containing systems with variable content of sulfate and selenate ions and with addition of mon-ovalent (K, Cs) and divalent (Mg, Zn) cations. During synthetic experiments, a number of phases have been detected, including those with novel structural topologies unprecedented among inorganic oxy-salts? as well as selective Se-for-S substitution depending on the coordination arrangement of tetrahedra have been shown.