@Mor - That's kind of a general diagnosis. While it probably was the smoke, it could also have been other things. It is terrible that your mother wasn't able to make her own choice about inhaling smoke. I'm glad that smoking inside is generally banned in most countries.
Lung cells are really delicate. I guess they have to be vulnerable to things like smoke, or they wouldn't be as effective at taking in oxygen.
You'd be surprised how often it happens that parts of the lung just up and die altogether from being mistreated for years.
Smoking is one way it can happen, but of course there are all kinds of contaminants that can potentially harm your lungs.