People whose fetish focuses on smoking, usually other people smoking, may be said to have a smoking fetish. More commonly people identify themselves as having a smoking fetish and seek out sexual material or partners that will let them experience the arousal associated with watching others smoke. Little is known about how common any fetishes are in the general population. But a study in 2007 which looked at Internet fetish communities and tried to estimate the relative popularity of one fetish over another reported that 18% of people who belonged to a fetish group had a fetish focusing on other people's behaviors, the category that most people with a smoking fetish would fall into.
As with most fetishes, there is an incredible range and variation among people with smoking fetishes. The focus of arousal, the thing that turns one on, may be related to a part of smoking activity (e.g. lighting a cigarette, inhaling, exhaling, playing with the smoke in the mouth). It might be tied to the way the cigarette is held, how long the ash is, when and how it falls. Smoking fetishes may have preferences for cigarette brands, and may have preferences for the person smoking (in terms of gender, clothing, visual style, etc…).
As with shoes, some people have pointed out that there is an aesthetics to smoking, a visual style or cool, that has been documented and enjoyed since photography and movie image technology began. What distinguishes thinking smoking "looks cool" from a smoking fetish is the element of intense sexual thoughts, feelings, and/or arousal.
It is interesting to consider the question of harm in terms of a smoking fetish. Many sex educators agree that fetishes can be a healthy part of sexual expression as long as engaging in them is consensual and doesn't interfere with your ability to live. While the smoking fetishist may or may not smoke, the person doing the smoking is risking their health in a well documented way. Which raises the question; can a smoking fetish ever be said to be "healthy"?
Scorolli, C., Ghirlanda, S., Enquist, M., et. al. "Relative Prevalence of Different Fetishes" International Journal of Impotence Research Vol. 19, (2007): 432-437.