During 34 years of smoking, Carolyn Smeaton has tried countless ways to reduce her three-pack-a-day habit, including a nicotine patch, nicotine gum and a prescription drug. But stop-smoking aids always failed her.

Image of an e-cigarette

Then, having watched a TV infomercial at her home here, Ms. Smeaton tried an electronic cigarette, which claimed to be a less dangerous way to feed her addiction. The battery-powered device she bought online delivered an odorless dose of nicotine and flavoring without cigarette tar or additives, and produced a vapor mist nearly identical in appearance to tobacco smoke.