The objective of this study was to develop an in vivo CT imaging-based approach for pulmonary arterial morphometry measurement, and to improve the geometrical basis for studies of the porcine vasculature. The luminal diameter and distance from the inlet of left and right pulmonary arteries, and pulmonary arteries within the lungs of two porcine subjects were measured at inflation pressure of 25 cmH(2)O. The results suggest that the porcine pulmonary arteries have geometric self-similarity, and that this approach will have utility for systematically quantifying pulmonary arterial vessel dimensions in vivo in a larger group of animals.