In a wireless LAN system according to the present invention, when a first communication station transmits packets to a second communication station, the first communication station can select a first method in which the second communication station returns first transmission-confirmation information to the first communication station for each packet that the second communication station receives, and a second method in which the second communication station returns, in response to the request of the first communication station, second transmission-confirmation information to the first communication station for plural received packets. The first communication station selects either one of the first method and the second method, based on a number k of packets to be acknowledged by the second transmission-confirmation information. With this arrangement, in the wireless LAN system capable of using plural kinds of transmission confirmation information, transmission confirmation information capable of improving transmission efficiency is selected.