CT imaging techniques permit the non-invasive measurement of regional lung function. Regional specific volume change (sVol), determined from the change in lung density over a tidal breath, should correlate with regional ventilation and regional lung expansion measured with other techniques. sVol was validated against xenon (Xe)-CT specific ventilation (sV) in four anesthetized, intubated, mechanically ventilated sheep. Xe-CT used expiratory gated axial scanning during the washin and washout of 55% Xe. sVol was measured from the tidal changes in tissue density (H, houndsfield units) of lung regions using the relationship: sVol = (1000 (Hi-He)) / (He (1000+Hi)) where He and Hi are expiratory and inspiratory regional density. Distinct anatomical markings were used to define corresponding lung regions of interest between inspiratory, expiratory, and Xe-CT images, with an average region of interest size of 1.6±0.7 ml. In addition, sVol was compared to regional volume changes measured directly from the positions of implanted metal markers in an additional animal. A linear relationship between sVol and sV was demonstrated over a wide range of regional sV found in the normal supine lung, with an overall correlation coefficient (R²) of 0.66. There was a tight correlation (R²=0.97) between marker-measured volume changes and sVol. Regional sVol, which involves significantly reduced exposure to radiation and Xe gas compared to the Xe-CT method, represents a safe and efficient surrogate for measuring regional ventilation in experimental studies and patients.