Background: We sought to determine if the acute gains in pulmonary arterial diameter achieved by using Cutting Balloons to dilate stenoses in small arteries are maintained at follow-up. Methods: A search of our database identified all patients who underwent dilation with Cutting Balloons for pulmonary arterial stenosis between June 2001 and September 2003. We reviewed the procedural and angiographic data obtained at the initial and follow-up procedures. Results: Over the period of study, 29 patients with a median age of 3.7 years, and a range from 0.4 to 46.6, underwent treatment with Cutting Balloons at 41 procedures for one or more pulmonary arterial obstructions resistant to conventional angioplasty. At the initial procedure, we enlarged 79 vessels, with an initial minimal luminal diameter of 1.5 plus or minus 0.8 millimetres, to a diameter of 3.0 plus or minus 1.1 millimetres (p smaller than 0.001). Angiographic data indicated that 49% of the vessels showed evidence of vascular damage not requiring intervention, while stents were placed in 9 vessels. Follow-up angiography was available for 39 of the vessels, evaluated at a median of 6 months, with a range from 3 to 24 months, after the initial procedure. In these vessels, there was a mean loss of 10 plus or minus 25% in luminal diameter, p not significant. Of the 39 vessels, 8 had returned to a diameter within half of the initial diameter, giving a failure rate at follow-up of 21%, with 95% confidence intervals from 9% to 36%. All complications were identified within 24 hours of the catheterization procedure, and there were no late complications or deaths during the period of follow-up. Placement of stents produced both greater increases in diameter at the initial procedure (p smaller than 0.001), and greater losses at follow-up (p equal to 0.01). Conclusions: Despite the frequent identification of intravascular trauma, initial gains in luminal diameter after use of Cutting Balloons to dilate stenotic pulmonary arteries are maintained at follow-up.