Optical splitters could decrease link cost and number of wavelengths used in an optical network. We address the efficient placement of splitters to minimize the global cost of optical links for a multicast session. We use a hierarchical structure (a form of optical tree in which a node can be visited more than once). Then, two algorithms are proposed to select a set of multicast capable nodes in order to minimize the global cost of links of a multicast session. Simulations results show also that the proposed algorithms are significantly better than the ND (node degree) algorithm with regard to number of wavelengths used and total cost of links.