The efficacy of medium-sized cutting balloons (CBs) 5 to 8 mm in diameter was compared with that of standard balloons (SBs) in the dilation of peripheral pulmonary stenosis (PPS). Nine vascular lesions in 7 patients were primarily dilated by CBs, and 13 vascular lesions in 11 patients were dilated by SBs alone. The efficacy of balloon dilation was evaluated by angiography and intravascular ultrasound (IVUS). There was no significant difference between the 2 groups in the success rate (66% vs 62%), the percentage increase in minimal lesion diameter (MLD; median 71% vs 52%) on angiography, and the number of new tears (2 vs 1) on IVUS. However, in the subgroup of vascular lesions with MLDs of <4.0 mm, for which CBs with diameters >200% of the MLD could have been applied, the percentage increase in MLD (95% vs 53%, p <0.05) and the number of tears (2 vs 1, p <0.05) with CBs were significantly greater than with SBs, requiring significantly smaller maximum balloon pressure (10 vs 13 atm, p <0.05). CBs are as effective as conventional balloons in the dilation of PPS and may be more effective when larger balloons are available.