— Without the multicast support from the underlying networks, overlay multicast has the advantage of implementing inter-domain multicast communications. Usually, overlay multicast protocols employ two different topologies: tree and m-D mesh. We propose to study the influence of topology selection to the multicast performances in this paper. We present a set of theoretic results on the metrics of the worst link stress, the worst number of overlay hops and the number of shortest paths for tree-based and m-D mesh-based multicast respectively. Then, we give our observations to these two kinds of multicast. To the best of our knowledge, we are the first to evaluate multicast performances on different overlay topologies. We hope that our results are useful for the new multicast protocol design. We hope that our results are useful for the design of new overlay multicast protocols.