The present invention relates to a for controlled synthesis of hydrogen-rich cyclosiloxanes of the (H.sub.2SiO).sub.n type. ##STR00001## where n is an integer equal to or greater than 3, by reacting: a.) a halosilane of the H.sub.2SiX.sub.2 type where X=halogen with b.) a lithium salt, copper(II) salt or a salt of a metal from main group 2 or transition group 2 of the periodic table of the elements, or a mixture of these salts. The ring size is advantageously adjustable to n=3, 4, 5, 6 (especially n=4 to 6), such that larger rings are not formed.In a particularly advantageous embodiment of the process, for the selective preparation of cyclohexasiloxane (H.sub.2SiO).sub.6, after the reaction, the solvent is at least partly removed and then solvent is added again.