The disclosed embodiments relate to a method for arranging the transfer of packets between a wireless data transfer device (MS) and a mobile communication network (NW). For transferring packets between the wireless data transfer device (MS) and the mobile communication network (NW), temporary block flows (UL TBF, DL TBF) are formed, and information is transferred in these block flows in one or more packet data traffic channels (PDTCH) either in the first direction from the mobile communication network (NW) to the wireless data transfer device (MS) or in the second direction from the wireless data transfer device (MS) to the mobile communication network. In the method, information about the end of the block flow is set in a packet to be transmitted in a block flow when data transfer has stopped. When the transfer of packets in said first direction has stopped, at least one enquiry message is also sent from the mobile communication network (NW) to the wireless data transfer device (MS). If there are packets to be sent to the mobile communication network (NW) in the wireless data transfer device (MS), a reply message to the enquiry message is sent from the wireless data transfer device (MS), which also sets information about the need to send packets in the reply message.