A ski boot comprising a conventional rigid sole from which there protrudes, from the area of the forefoot and approximately up to the area of the arch of the foot, a shell open in the direction of the area of the heel of the sole, thereat and to which there is rearwardly and slideably connectable a buttress element interacting with adjustment and guiding elements of the axial position with respect to the sole and to which a height-adjustable cuff is rotatably connectable.