Abstract: A chair seat adapted to be mounted on or in a frame, and comprising a seat part (4) and a backrest part (5), which parts are functionally separate units, and which are joined by a spring means which allows the backrest part to move resiliently in relation to the seat part, and in which the spring means comprises one or more thin flexible strips of a spring material, preferably a carbon fibre web material, comprising a flat upper spring part (2a) which is fixed to the backrest part (5) of the chair seat and a flat lower spring part (2b) which is fixed to the seat part (4) of the chair seat, and in which the spring means (2) is formed with a curved spring part (8) between the two flat spring parts (2a, 2b) which is substantially free from the seat and the backrest, and which provides a spring action and a counter spring action of the backrest (5) in relation to the seat part (4).