Our recent theoretical and/or Monte Carlo (MC) studies of dilute solution properties of semiflexible stars and rings are briefly summarized. The theoretical results for the intrinsic viscosity [eta] of the Kratky-Porod (KP) wormlike three- and four-arm stars are shown, and effects of chain stiffness on [eta] of the stars are examined. A comparison of the results for [g] with those for the effective hydrodynamic radius and the second virial coefficient A(2) in a good solvent was made for the semiflexible three-arm stars. It was found that [eta] is the most suitable object of study to examine the effects of chain stiffness on average chain dimensions of the stars. As for the rings, the MC results for A(2) of the ideal KP rings, which is related to the intermolecular topological interactions, are presented and then compared with the data in the literature for ring atactic polystyrene (a-PS) at Theta for large molecular weight M (1 x 10(4) -6 x 10(5)). Even for ring a-PS in such a range of M, the effects of chain stiffness were still remarkable. The effects of the intramolecular topological constraints on the mean-square radius of gyration and the scattering function of the KP rings are also discussed.