BACKGROUND: Both single and bilateral lung transplantation are recognised options for patients who have end-stage chronic obstructive pulmonary disease (COPD); however, which procedure leads to longer survival remains unclear. We aimed to compare survival after each procedure by analysing data from the registry of the International Society for Heart and Lung Transplantation. METHODS: We analysed data for 9883 patients with COPD, 3525 (35.7%) of whom underwent bilateral lung transplantation, and 6358 (64.3%) single lung transplantation, between 1987 and 2006. We accounted for possible selection bias with analysis of covariance, propensity-score risk adjustment, and propensity-based matching. FINDINGS: Median survival after either type of lung transplantation for patients with COPD was 5.0 years (95% CI 4.8-5.2). Survival for patients who had lung transplantation before 1998 was 4.5 years (4.3-4.8), compared with 5.3 years (5.0-5.5) for those who had it after 1998 (p<0.0001). The proportion of patients who had bilateral lung transplantation increased from 101/467 (21.6%) in 1993 to 345/614 (56.2%) in 2006. Median survival time after bilateral lung transplantation was longer than that after single lung transplantation: 6.41 years (6.02-6.88) versus 4.59 years (4.41-4.76) (p<0.0001). Pretransplant characteristics of patients who had single and bilateral lung transplantation differed, but whichever method was used to adjust for baseline differences, bilateral lung transplantation was associated with longer survival than was single lung transplantation; the hazard ratio ranged from 0.83 (0.78-0.92) for analysis of covariance to 0.89 (0.80-0.97) for propensity-based matching. However, bilateral lung transplantation had little benefit compared with single lung transplantation for patients who were 60 years and older (HR 0.95; 0.81-1.13). INTERPRETATION: Bilateral lung transplantation leads to longer survival than single lung transplantation in patients with COPD, especially those who are younger than 60 years.