I read somewhere (I don't remember the source, but it was some medicine journal) that 4% of smokers are genetically more inclined to die from lung cancer; while lung cancer is correlated with the number of cigarettes (intensity and length of time), these people will have lung cancer even with a very low number of cigarettes.

I know a few anecdotal cases where entire families of smokers died from lung cancer, while their partners, also smokers, had no problem, but I don't put much weight on that. Also I heard that smoking can cause other cancers like colon cancer in specific genetic conditions, but I don't know more details.