An apparatus for forming an absorbent pad (100) for an absorbent sanitary article having at least one zone (Z1, Z2) free of absorbent material (103) and intended to define a respective channel (104, 105) of the pad (100)； the apparatus comprises a forming drum (2), a first feed system (4) for feeding a first web (NW1), a second feed system (5) for feeding a second web (NW2), at least one spreader (6) for spreading the absorbent material (103) on the forming drum (2)； a joining system (15) for joining the first and second webs (NW1, NW2) at least at the zones (Z1, Z2) free of absorbent material (103) to define the channels (104, 105) of the pad (100)； the apparatus (1) comprises a first dispenser (9) of a first adhesive substance (10), configured to create on the first web (NW1) a layer (110) of the first adhesive substance (10) according to a spreading pattern (M2) having zones (S1, S2) free of the first adhesive substance (10) corresponding to the zones (Z1, Z2) free of the absorbent material (103) and a second dispenser (11) for dispensing on the second web (NW2) a second adhesive substance (12), whose adhesive force is greater than the adhesive force of the first adhesive substance (10), and configured to spread the second adhesive substance (12) on the second web (NW2) according to a spreading pattern (M3) having at least one layer (112) of the second adhesive substance (12) intended to be placed at least at a respective zone (S1, S2) free of the first adhesive substance (10).
