19F-MRI of inhaled perfluoropropane can be used for assessment of pulmonary ventilation. Static breath hold 19F-MR images were acquired pre- and post-bronchodilator following inhalation of a perfluoropropane/oxygen gas mixture in patients with asthma and patients with chronic obstructive pulmonary disease (COPD). Percentage ventilated lung volume (%VV) was calculated from each of the 19F-MR images. %VV was significantly reduced in both patient groups, and between pre- and post-bronchodilator acquisitions in the asthmatic patient group. A strong positive correlation between %VV and spirometric indices was revealed. Gas inhalations were well tolerated by all participants, with no adverse events.