How long does it take a cigarette butt to decompose?

Cigarette butt : 18 months - 10 years

Cigarette Butts are made of plastic, of the same type of plastic as is found in plastic bags and soda bottles. They will eventually degrade, especially if the environment is right for that sort of thing (moist, warm, and shady) but they will take much longer to degrade if flicked away on a beach or some other sandy, dry, hot area. The nicotine contained in 200 leftover cigarette butts, however, is enough to kill a full-sized human being (according to the admittedly biased http://www.whyquit.com/), and can have a negative impact on the wildlife in the area.