Light cigarettes are a product of the tobacco industry’s attempt to market what looked like a safer cigarette back in late 1960s. The difference between light and regular cigarettes lies not in the tobacco each contains, which is identical, but in the filters. Light ones generally have filters covered in white paper rather than the tan or cork-patterned paper of regular cigarettes. This color difference, however, is not a critical one.
The distinction that matters is harder to discern and has to do with ventilation: the paper covering of light cigarette filters has many tiny little holes punched in it. Under laboratory conditions, these perforations cause the proportion of air in each draw on the cigarette to be higher than that in a draw on a regular one. For a person accustomed to regular cigarettes, in fact, these multiple small punctures can make it difficult to draw adequate smoke.
More than 80% of the cigarettes sold in the United States are light cigarettes, also called low-yield cigarettes. People may prefer them to regular, or full-flavored, cigarettes because the diluted smoke they produce seems smoother and less dense, and therefore feels less irritating to the throat. The filters of ultra lights have even more holes than do those of lights and so create even thinner smoke. Most full-flavored cigarette brands have light counterparts, while some cigarettes exist only in light or ultra light versions.
A preference for light cigarettes may also derive from the notion that they are less harmful than regular cigarettes. The smoke is diluted, and this results in lower lab readings of tar, nicotine, and other components. The measurement of tar in lab tests of ultra lights ranges from 1-6 mg; lights can have anywhere from 6-15 mg of tar; more than 15 mg of tar qualifies a cigarette as regular. Because of the way people actually smoke, however, the lower numbers of lights and ultra lights may not be realized in practice.
The fingers and lips may block the perforations left unimpeded by the smoking machine used in the tests so that the proportion of air to smoke is not as high as it would be under ideal conditions. More significantly, people who smoke will do so until their craving for nicotine is sated, and that could mean smoking more cigarettes to compensate. There are no demonstrable health benefits in smoking light rather than regular cigarettes. For this reason, Canada and the countries of the European Union have banned cigarette manufacturers from labeling their products as "light."