Impedance measurements of the respiratory system by means of the forced oscillation technique were performed in a group of 20 COPD patients before and after inhalation of 0.400 mg salbutamol. A slight, but statistically non significant decrease of resistance is observed at all frequencies from 12 to 52 Hz. Increase of reactance values reached a statistically significant level at all frequencies except at 24 and 52 Hz. It is hypothesized that the increase of reactance in these patients can be explained by an increase of capacitance due to an increase of airway compliance or a decrease of peripheral resistance according to Mead's analogon of the lungs.