Introduction: Considering a common embryologic origin of the aortic (Ao) and pulmonary artery (PA) roots, similar histopathological changes of the ascending aorta could exist in the PA media in patients (pts) with bicuspid aortic valve (BAV). Although studies have shown that Ao elasticity is impaired in BAVs, there are currently scarce data on PA stiffness in these pts. The purpose of the present study was to assess the elastic properties of the ascending aorta and pulmonary trunk in BAVs. Methods: 37 BAV pts (39 ± 14 years, 27 men) and 30 control subjects (43 ± 15 years, 16 men) with similar age, gender and bodysize were enrolled. Exclusion criteria were inadequate acoustic window, right chambers dilation/dysfunction, PA hypertension or disease. The cut-off values used to define dilated ascending aorta (AoA) and PA were >36 mm and > 23 mm, respectively, measured at end-diastole. The elastic properties of the Ao derived by systolic and diastolic AoA diameters together with sphygmomanometer-based brachial blood pressure measurement. Ao elastance: Ea = (Systolic BPx0.9)/SV, SV-stroke volume. PA indexes of stiffness were measured using end-diastolic and end-systolic PA areas. PA stiffness: PAS = MFS/AcT, MFS – maximal frequency shift , AcT – acceleration time. Results: BAVs had higher dimensions of the Ao annulus, AoA and PA (p < 0.001). Pts with dilated AoA had also a dilated PA (p = 0.021). At univariate analysis, the PA diameter correlated with dimensions of Ao annulus (r = 0.5, p < 0.001), sinotubular junction (r = 0.47, p < 0.001), and AoA (r = 0.42, p = 0.008). In BAVs, Ao strain (3.6 ± 2.1 vs 4.7 ± 2.5%, p=.051) and elastance (1.2 ± 0.4 vs 1.6 ± 0.3 mm Hg/ml, p < .001) were lower, while Ao elastic modulus (19.1 ± 10,2 vs 13.7 ± 8.1 mm Hg, p = .022) and stifness index (20.2 ± 9.9 vs 14.6 ± 8.4, p = .018) were greater. In BAVs, PA strain (7.9 ± 4.0 vs. 12.7 ± 8.25%, p = .003) and dynamic compliance (27.5 ± 13.1 vs 46.3 ± 32.1 mm Hg-1, p < .002) were lower, while elastic modulus (103.6 ± 46.8 vs 72.3 ± 44.2 mm Hg/ml, p = .007) and PAS (16.9 ± 3.2 vs 14.2 ± 3.4 kHz/ sec., p = .015) greater. Conclusions: In BAV pts, PA dilation coexists with ascending aorta dilation. Elastic properties of the PA tend to be impaired in BAV pts as in the aorta in this setting. Measuring aortic and PA elasticity may help to identify pts at greater risk for further complications.