The invention relates to a head support device (19) attached to a treatment table (12). The treatment table comprises a back portion (13) pivotably joined to a seat portion (14). The head support device (19) is attached to the back portion (13) and has a head support bowl (18). The head support device (19) has a head support sled (32) arranged in a first bearing for linear forwards and backwards movement in a carrier unit (31) in the head support device (19). The head support device (19) is provided with a weight balancing unit (61). Through the weight balancing unit is achieved that the head support device is experienced by a user as being weightless or floating. The invention further relates to a back portion provided with such a head support device (19), and a treatment table (12) provided with such a head support device (19).
