Six new star-shaped polydimethylsiloxane (PDMS) with various cyclic siloxane cores were synthesized by the "grafting onto" method. The polymers obtained feature low dispersity and well-defined structures. Two of them, Q(8)-PDMS and D-12-PDMS, have a three-dimensional spatial structure traditional for star-shaped polymers where the arms are arranged in all directions from the branching center. The other four polymers, D-4-PDMS-D-8-PDMS, have quite a different spatial geometry (cis-structure) where all the PDMS-arms are arranged on one side of the branching center plane. Such star-shaped structures were not reported before. The structures and purity of the polymers obtained were confirmed using a set of physicochemical methods of analysis. The effect of the macromolecule structure on the properties of the target polymers was identified. (c) 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019