Lung morphometry parameters can be derived from multiple b-value hyperpolarized gas diffusion-weighted (DW)-MRI using the cylinder (CM) and stretched exponential (SEM) models. Mean alveolar diameter (LAlv) and diffusive length scale (LmD) are calculated from the CM and SEM, respectively. This work compares the parameters LAlv and LmD derived from a range of subjects with both 3He and 129Xe DW-MRI. Excellent linear agreement is observed between the LAlv and LmD parameters for both gases. This indicates these parameters are equivalently representative indices of mean alveolar diameter dimension within the range of experimental conditions considered.