Some 3.7 million people in the UK are believed to have a condition that causes a persistent cough, chest infections and chest pain – but only 900,000 are currently diagnosed, the British Lung Foundation has said.
Chronic obstructive pulmonary disease (COPD) affects many smokers and quitters and the foundation is urging these groups to get tested for it.
Dame Helena Shovelton, Chief Executive of the British Lung Foundation, said: "Symptoms such as breathlessness and a persistent cough are often ignored by smokers or ex-smokers as signs of getting older, but they could be symptoms of COPD.
"COPD is a chronic, irreversible disease that can leave individuals unable to perform simple everyday tasks and dependent on oxygen."
A survey of more than 400 people for the foundation found that 73% of those asked had not had a lung-function test, but 21% said they had been experiencing COPD symptoms.
Some 8% said they had to stop and take a breath when they were walking on flat ground. Almost one in five (19%) said they felt breathless walking up a slight hill.
The British Lung Foundation is urging people to have a 10-minute lung function test, which is painless.