Small-angle diffraction of polarized neutrons and resonant contribution to diffraction of synchrotron radiation have been applied to prove chirality of the crystal and magnetic structures of the magnetoelectric insulator Cu2OSeO3. Similarly to other chiral magnets with P2(1)3 crystal structure the corresponding chiralities are linked to each other via the phenomenological Dzyaloshinskii-Moriya interaction. The crystal and magnetic structures for Cu2OSeO3 have the same chirality as is observed for MnSi, Mn1-x Fe-x Si, and MnGe. However, the combination of chiralities is opposite to that proposed from a recent theoretical consideration. The chiral link between structure and magnetism previously found for metallic compounds is also proved to exist for an insulator (Cu2OSeO3), allowing us to conclude that the conducting electrons play no role in a possible common microscopic mechanism of this specific magnetolattice interaction.