The invention relates to group communication services, i.e. communication services involving two or more users (or service participants). The invention provides a method for distributing multicast data of a multicast service to different domains and a method for distributing multicast data to service participants in a domain. Further, the invention relates to a control node and system implementing the respective methods. To improve resource utilization when providing a multicast service, including inter alia PoC services, to service participants the invention provides mechanisms to avoid unnecessary multiplication of multicast data in the distribution tree for multicast services with service participants of different domains. For this purpose the controlling node that is initiating the multicast service upon request determined to which domains the multicast data is to be provided and only forwards the multicast data on a per-domain basis. Another aspect of the invention is the avoidance of unnecessary duplications of multicast data within individual domains.