Prevention of chronic obstructive pulmonary disease hospital readmissions is an international priority aimed to slow disease progression and limit costs. Evidence of the risk of readmission and of interventions that might prevent it is lacking. We aimed to determine readmission risk for chronic obstructive pulmonary disease, factors influencing that risk, and variation in readmission risk between hospitals across 7.5 million people in London. This retrospective longitudinal observational study included all chronic obstructive pulmonary disease admissions to any hospital in the United Kingdom among patients registered at London general practices who had emergency National Health Service chronic obstructive pulmonary disease hospital admissions between April 2006 and March 2010. Influence of patient characteristics, geographical deprivation score, length of stay, day of week of admission or of discharge, and admitting hospital, were assessed using multiple logistic regression. 38,894 chronic obstructive pulmonary disease admissions of 20,932 patients aged ≥ 45 years registered with London general practices were recorded. 6295 patients (32.2%) had at least one chronic obstructive pulmonary disease readmission within 1 year. 1993 patients (10.2%) were readmitted within 30 days and 3471 patients (17.8%) were readmitted within 90 days. Age and patient geographical deprivation score were very weak predictors of readmission. Rates of chronic obstructive pulmonary disease readmissions within 30 days and within 90 days did not vary among the majority of hospitals. The finding of lower chronic obstructive pulmonary disease readmission rates than was previously estimated and the limited variation in these rates between hospitals suggests that the opportunity to reduce chronic obstructive pulmonary disease readmission risk is small. CHRONIC LUNG DISEASE LOWER RISK OF READMISSION FOR LONDON-BASED PATIENTS: A managed reduction of hospital readmissions for London-based chronic lung disease patients may not be needed. Preventing hospital readmissions for patients with chronic obstructive pulmonary disease (COPD) is a key priority to improve patient care and limit costs. However, few data are available to determine and ultimately reduce the risk of readmission. Timothy Harries at King's College, London, and co-workers conducted a longitudinal study incorporating all COPD admissions into UK hospitals for 20,932 patients registered at London general practitioners between 2006 and 2010. They found that 32% of patients were readmitted within a year, 17.8% within 90 days and 10% within 30 days. Neither age nor geographical deprivation were useful predictors of readmission. These represent lower than estimated levels of readmission, suggesting there may be fewer opportunities to reduce the risk of readmission further.