Abstract: This invention relates to an adjustable chair comprising a frame supporting a seat pivotable with respect to the frame and a back, said chair further comprising a calf support arranged at the forward end of the seat and displaceable between a retracted position in which it is positioned substantially under the seat, and an extended position in which it forms a substantially straight extension of the seat; and a chair adjusting mechanism comprising a drive means provided with a supporting surface, which drive means through a movement such that the seat slides with respect to said supporting surface brings the seat into different using positions so that when the calf support is positioned in its retracted position, the seat forms a less tilted positioned than when the foot support is positioned in its extended position.