In most yaoi/shounen-ai manga, the seme is the one who smokes. I want to read one where it's the uke who has the smoking problem and the seme tries to get him to stop. Like some scenarios could be like...

-The seme maybe was in the uke's position before so he understands why the uke is smoking and is determined to help/save the uke.

-The uke is giving up the hope for life and is turning to smoking/doing drugs for a way out and the seme tries to change him.

Stuff like that. It doesn't have to be smoking. It could be getting high or other stuff with drugs or having a drinking problem. Not so much the uke having sex to forget his painful past or having a sex problem.

BrandNewWings

It's been a while since I read these but I filtered them with a Smoking as a category so it may or may not have what you're looking for:

Saezuru Tori wa Habatakanai (uke smokes but I don't think the seme ever tried stopping him -- would you seriously try to stop a yakuza as an underling?)
Himegoto Asobi (just look at that cover, totally what you're looking for)
Doushitemo Furetakunai
Sojou no Koi wa Nido Haneru
NightS