The objective of the present study was to compare the immediate result of laser-assisted piston stapedoplasty with the use of prosthetic stapes of different diameter in the patients with otosclerosis. The patients of both (study and control) groups underwent the measurement of the bone conduction (BC) auditory threshold before, 10-12 days, and 1 month after surgery. The bone-air interval (BAI) was measured in the same time periods. A CO2 laser was used to form a hole 0.5 mm in diameter at the base of the stirrup bone in the patients of group 1; titanium prostheses (Heinz Kurz GmbH) were 0.4 mm in diameter and 4.25 mm in length. The patients of group 2 were treated similarly, but the hole at the base of the stirrup bone had a greater diameter of 0.7 mm while the prostheses were 0.6 mm in diameter and 4.25 mm in length. The BC auditory thresholds were not significantly different after surgery in the patients of A and B subgroups (mixed forms I and II of otosclerosis, respectively). The postoperative BAI values in the patients with a larger hole at the base of the stirrup bone and prostheses of greater diameter were significantly lower than in the patients of the other group (p≤0,05). These data suggest that the use of prostheses of greater diameter has certain advantages for stapedoplasty by the methos employed in the present study.