Smoking unequivocally causes damage to the lungs.
Smoking is a massive risk factor in the development of cardiovascular disease and it dramatically increases your chances of developing lung cancer.
Normal, well functioning lungs are essential for safe diving to minimise the chance of pulmonary barotrauma (burst lungs).
The simple advice is to STOP SMOKING. Your GP or local NHS stop smoking service can provide you with support.
If you have suffered ill health and smoking has been implicated as a factor (e.g. a heart attack), there is very little chance you will be found fit to dive unless you have stopped smoking.
Vaping
Vaping is less harmful than smoking but it is not risk free. Vapes often contain high levels of nicotine which is a highly addictive drug (a UK standard disposable vape delivers a similar amount of nicotine as 20 cigarettes).
As vaping is relatively new, the long term effects on the lungs are not well understood. For divers, vaping can be a useful tool to stop smoking but ultimately the best way to look after your lungs is to avoid smoking and vaping.