This paper presents the analysis of the multicasting perfor-mance in broadcast-and-select wavelength division multiplexing (WDM) networks from two aspects: multicast session length and multicast group size. The protocol analyzed in this paper is based on a combinational protocol to schedule unicast and multicast traffic. The packet distance, determined by the Euclidean distance of session length and the group size of a multicast packet, is compared with the multicast distance to select the most appropriate scheduling method for multicast packets. Comparisons on channel utilization and packet delay further show that the session length will affect the channel dominance significantly and the group size will determine the range of multicast distance such that the performance metrics will remain the same. In addition, multicast traffic with larger mean session length or mean group size will make some specific scheduling strategies fail to achieve optimal performance. If the multicast distance is properly chosen, performance tradeoffs can be made under the multicasting environments with large session length or large group size.