OBJECTIVE: to verify the functional result after estapedotomy, in accordance with the diameter of prosthesis (0,6 or 0,4 mm), in patients with otosclerosis. MATERIALS AND METHODS: evaluated, retrospectively, postoperative audiometry daily pay and of 108 submitted patients the estapedotomy with prosthesis of teflon of 0.4 and 0.6 mm, between 2008 and 2011, in the Santa Casa Hospital of Belo Horizonte. Arithmetic means of the tonal thresholds for by airmail and osseous in the 3000 frequencies of 500 had been made Hz. Calculated, then, aerial-osseous GAP and profit by airmail postoperative daily pay and. The improvement was evaluated by postoperative GAP (GAPPO) e, to evaluate the relation between the same and the type of prosthesis was used chi-square test. RESULTS: of the 108 evaluated patients, 72 (66.7%) were of the feminine sex, the average of the ages were 43,85 years (shunting line standard: 10,85). The average of the aerial profit was of 30 dB and of the GAPPO of 8dB. In the 73 (67,6%) patient 10 GAPPO he was ≤ dB; in 28 (25,9%) it was remained enters 10 and 20 dB and >20 dB in 6 (5,6%) patient ones. Information on the diameter of the prosthesis had been found in 80 handbooks and, in 56,8% of them were used of 0.6mm. Difference was not found significant enters the type of prosthesis and GAPPO of these patients (p=0,15). CONCLUSION: the study reaffirms the advantage of the estapedotomy in the treatment of patients with otosclerosis and suggests that does not have difference in the audiometric results in relation to the diameter of prosthesis used (0,4 or 0,6 mm). However, new studies still need to be carried through.