Information checked against current lung-health guidance: 7 October 2026.

It’s common knowledge that smoking damages the respiratory system.  If you’re a smoker you’ll have noticed that you cough frequently and may suffer from breathlessness.

That’s a sign that smoking is affecting the health of your lungs and that you may have developed a respiratory condition as a result of your habit. 

You may also have seen images showing the difference between the healthy lungs of a non smoker, compared to the blackened and unhealthy lungs of a non-smoker. But do you know why smoking is so bad for your lungs?

In this article we’ll explain why smoking harms the respiratory system and how quitting the habit will benefit your respiratory system.

How does smoking affect the lungs?

The lungs are lined with cilia – little hair like structures that do the important job of sweeping particles out of your airways. Smoking damages the cilia and stops them from working properly

Smoking causes the airways to become inflamed and to produce more mucus which can lead to a chronic cough.

The airways also start to narrow as a result of the damage caused by smoking, making it harder for air to flow in and out of your body, leading to breathlessness.

This shortness of breath is a symptom of chronic obstructive pulmonary disease (COPD) – a group of lung conditions that cause shortness of breath, including chronic bronchitis and emphysema.

Your lungs contain air sacs called alveoli which transfer the oxygen you breath in to your bloodstream. Smoking destroys the alveoli meaning the lungs are less able to provide your body with oxygen, a condition called emphysema.   As the condition progresses you will find it more difficult to take part in physical activities and may even feel short of breath while resting.  Your brain function will also be affected as it will be receiving less oxygen than it needs.

Smoking is the leading cause of lung cancer which develops when toxic substances contained in cigarette smoking cause the cells in the airway to become malignant.

Smoking is the most common risk factor for COPD. Asthma + Lung UK says around 9 in 10 cases of COPD are linked to cigarette smoking. Smoking is also a major cause of lung cancer. If you want more detail about COPD and quitting, see our smoking and COPD guide.

Smoking can make existing lung conditions harder to manage. Stopping smoking can improve lung function, reduce symptoms such as breathlessness, coughing and wheezing, and reduce the risk of COPD flare-ups and respiratory infections.

The benefits of quitting smoking

After just one month of giving up smoking, your lung function will start to improve. As the lungs heal you will start to cough less and breathlessness will improve. You may find yourself better able to take part in physical activities.

Lungs that have been severely damaged by smoking cannot return to normal if you quit. However, by giving up you will prevent diseases such as COPD getting worse and further affecting your quality of life

When you stop smoking, you reduce your chance of developing lung cancer. After 15 to 20 years your risk of developing lung cancer will be reduced by 90% compared to those who continue to smoke.

If you are a smoker who would like to access free help and advice on how to quit smoking, then contact NHS Wales Help Me Quit service.