OBJECTIVE: To determine the reliability of Computed Tomogram angiography (CTA) in evaluating pulmonary artery (PA) morphology compared to conventional angiogram. METHODS: This prospective observational study involved 36 patients with cyanotic heart disease from July 2006 to June 2008. The CTA and conventional angiogram were performed in patients in whom the PA was not well visualized on conventional angiogram or; as part of routine pulmonary artery assessment post PDA stenting . The size of right (RPA) and left (LPA)pulmonary artery diameters were measured on both modalities. Branch pulmonary arteries were classified as either confluent, stenosed (defined as ≥ 50% narrowing) or absent. The investigators reporting the CTA are blinded of the angiogram findings. The findings on both modalities were compared. The sensivity and specificity of CTA were mesured based on the the ability to demonstrate the significant stenosis or absent pulmonary artery. RESULTS: Branch PA was not visualized (absent) in 12 patients on conventional angiogram, but all were visualized on CTA. Branch PA stenosis was reported in 3 patients on CTA, 3 patients of conventional angiogram and 4 patients on both modalities. The mean RPA diameter measured by angiogram and CTA were 10.1 ± 4.04 mm and 9.53 ± 4.67 mm respectively (p=0.22) The mean LPA size measured by angiogram and CTA were 7.51 ± 4.16 mm and 7.95 ± 4.74 mm respectively (p=0.61). The sensitivity and specificity of CTA were 70% and 94% respectively. CONCLUSIONS: CTA is superior to conventional angiogram in evaluating pulmonary artery morphology.