Aims: A renewed interest in lung age is evidenced by recent smoking cessation publications. This research compares the original Morris lung age equations (1985) with contemporary Australian lung age equations. Methods: Both lung age equations were applied to the spirometry results of two sub-groups (never-smokers n=340, and current smokers n=50) from an independent dataset. Means of both lung age estimates were compared to the mean of the chronological age of each group by paired Student's t-test. Results: The Morris lung age estimates were paradoxically lower (younger) than chronological age in both groups. The new Australian equation produced lung age estimates that were equivalent to chronological age in the never-smoker group and significantly higher (older) than chronological age in the current smoker group. Conclusions: These results strongly suggest that the Morris lung age equations are in need of review. The use of contemporary lung age equations may translate into greater success for smoking cessation programs. The new Australian equations seem to possess internal validity.