FIELD: physics.SUBSTANCE: unit for photodynamic therapy of tumours of head and neck skin contains the laser radiation source with the light guide which regulates a light dose and a plate (8) on a frontal holder (6). The fixture for protection of healthy skin from laser radiation is designed as three parallel flat disks (15, 16) and is fastened with a possibility of fixing in a standard position through the transitional device (11) on the frontal holder (6). Disks (15, 16) have a common central axis. External disks (15) are rigidly connected to each other along the perimeter forming a blind cavity connected to the transitional device (11). The internal disk (16) is designed with smaller diameter compared external disks (15), fixed on the common central axis with a possibility of rotation and divided into equal sectors. In each sector the individual through hole (18) of pre-set diameter is made. The centres of holes are located from a rotation axis at a minimum allowable distance. In each external disk (15) there is a coaxial hole designed as a sector the central angle of which is equal to the central angle of the internal disk sector. The transitional device (11) is designed as metal parallel plates (12). Plates (12) have a shape of an equilateral triangle with depressions in their tops. In one of tops the hinge (9) of the metal rod connected with the plate (8) of the frontal holder (6) is fixed, in the second top - the hinge of the metal rod (10) connected with the adaptation for protection of healthy skin from laser radiation, and in the third top - the hinge of an additional metal rod (5) on which clamps (4) for fixing of the laser light guide are rigidly fixed. One clamp (4) is fixed on an additional metal rod (5) in such a way that the axis of rotation of lips of this clamp is at the level of hole sector top in external disks, and the axis of rotation of lips of another clamp (4) is located from the axis of rotation of lips of the first clip (4) at the distance
