To improve the definition of the geometrical and mechanical properties of the porcine pulmonary arteries, we utilized an <i>in vivo</i> imaging-based approach to quantify the influence of static extravascular pressure change on pulmonary arterial geometry. The cross-sectional area and distance from the inlet of pulmonary arteries of two animals were measured over a range of static airway inflation pressure (7 cmH<sub>2</sub>O - 25 cmH<sub>2</sub>O, i.e. 0.69 kPa – 2.45 kPa). Vessels with diameter range of approximately 2.0 mm to 5.5 mm at airway inflation pressure of 25 cmH<sub>2</sub>O (2.45kPa) were considered. The results suggest that lung inflation stretches the vessels laterally, but has no statistically significant effect on diameter.