Background and objective: The effects of bronchoscopic lung volume reduction (BLVR) on pulmonary ventilation and perfusion are incompletely understood. In this pilot trial, we investigated serial changes in regional ventilation and perfusion following unilateral endobronchial valve placement in COPD patients with heterogeneous emphysema. Methods: At baseline and at days 30 and 90 following BLVR, subjects underwent lung function, 6MWD and St George's Respiratory Questionnaire. Ventilation and perfusion scintigraphy were performed to quantitate and serially compare regional differences. Results: Six out of eight subjects completed the study; all had endobronchial valves targeting their left upper lobe. At day 90 post-BLVR, there was a trend towards an increase in FEV1 and a mean reduction in St George's Respiratory Questionnaire score of nine units. In the targeted left upper zone there was reduced ventilation and perfusion. Ventilation and perfusion to the right lung; and specifically the right lower zone, significantly increased. Conclusions: There appears to be redistribution of ventilation and perfusion to the contralateral lung following endobronchial valve placement. This may be of importance when assessing patients for unilateral BLVR. Selecting patients with heterogeneous disease is emphasized, taking into consideration not just comparison between upper and lower lobes, but between left and right lungs. A larger trial is currently underway, guided by these findings.