A first playback device, while operating in a first media playback system, receives from a computing device over a WAN an indication that a second playback device operating in a second media playback system has initiated sharing of a playback session. The first playback device transmits a request to join the playback session, and then receives, from the computing device over the WAN, playback session information including indications of (i) one or more media items in a queue designated for playback by the second playback device and (ii) a playback position of the second playback device within the one or more media items. The first playback device retrieves, from a media service, the one or more media items in the queue designated for playback by the second playback device. The first playback device then plays back the one or more media items beginning at the playback position.