This is an international, mulitcentre, observational, prospective study into Peak Inspiratory Flow in COPD patients that aims to: A) Determine the prevalence of suboptimal Peak Inspiratory Flow (PIF) and inadequate inhaler choice and assess the baseline characteristics of these groups. B) Assess the clinical role of PIF and inhaler choice in predicting COPD exacerbations and symptom burden. C) Assess the variability and correlation of PIF with other lung function measurements and CAT score in stable COPD. It is a 12 month study comprising one baseline assessment and 2 follow-up visits at 6 and 12 months.

Inclusion Criteria:

1. Spirometry-defined COPD (i.e. post-bronchodilator FEV1/FVC<0.7)
2. Age ≥40 years
3. Smokers or ex-smokers of at least 10 pack-years
4. Clinically stable COPD (no exacerbations in the last 4 weeks)
5. Capable of performing serial lung function tests
6. Prescribed inhaled medication for at least 6 months

Exclusion Criteria:

1. Occurrence of an COPD exacerbation during the previous 4 weeks
2. Have any concomitant chronic respiratory condition other than asthma or bronchiectasis (e.g. cystic fibrosis, lung fibrosis, tuberculosis)
3. Are unable to understand the instructions of the study or to fill the questionnaires
4. Are unwilling to sign the informed consent
5. Are participating in a clinical trial

COPD patients, who are clinically stable (4 exacerbations in previous 4 weeks) and have been taking inhaled medications for at least 6 months, but have no other chronic respiratory conditions, other than asthma or bronchiectasis.