Synthesis of a versatile hydroxysilylation agent and its use in the preparation of hydroxy derivatives of a poly(allylcarbosilane) dendrimer and hyperbranched polymer are reported. In a first approximation, the bulk properties of synthesized hydroxy polymers are found to essentially identical. Infrared spectroscopy provides evidence for the build-up of a complicated H-bond network in these polymers. Spectroscopic study of the hydroxyl groups can gain a deeper insight into the properties of branched dendrite-core macromolecules.