It doesn't happen often lately, but once in a while I will show a home that is very heavy with old, rancid smelling cigarette smoke. It really hits you when you walk in the door, and personally, I can't wait to get out of those homes, and in most cases my buyers feel the same. I've had buyers that have been so turned off by this that they won't even consider the home, even though it might be very nice and otherwise fit them.
I always give feedback (when requested) regarding this issue, and I can only hope those sellers will do something to mitigate the thick smoke odor in their homes. We had a listing of an Orland Park condo for sale and we noticed the smoke right away. The seller cleaned the carpets but it didn't get rid of it all. They cleaned them a 2nd time and it helped a bit, but I feel the walls needed to be painted (and there are paints now that have deodorizing properties), and the seller (an executor taking care of an estate) did not want to paint. He would try to drive over to the unit and air it out and use spray room fresheners before each showing. Luckily, with our marketing we got it sold, but it took a while and the price was less than the seller anticipated.
Smoking can be costly in many ways, but a lot of smokers do not realize it can also cost them when selling a home. What you should do if you're a smoker is immediately stop smoking inside the home. You will probably need to repaint the home (smoking also leaves walls dingy and sometimes speckled with yellowish spots) including ceilings. And you should have your carpets professionally cleaned using a deodorizer. You might also need to wash all bedding, especially comforters in guest rooms that have absorbed smoke odors, and maybe even some clothing that hasn't been washed recently. You should also get your upholstered furniture professionally cleaned and wipe down leather or vinyl furniture and possibly even wood.
I always caution buyers against buying on a busy street, near a train or a commercial area, etc., but I usually don't have to say anything about a house that smells like old cigarettes. Don't sell yourself short, getting rid of smoke is something every smoking seller needs to do to make their home more appealing.