On November 27, 2001, the U.S. National Cancer Institute (NCI) released a comprehensive new report detailing the 50-year history of light and low-tar cigarettes and their impact on the public's health. The report is the most comprehensive and conclusive ever, showing that there is no health benefit to smoking light and low tar cigarettes. In other words, smoking "light" cigarettes carries the same risk of lung cancer, heart attacks and other tobacco-caused disease as regular cigarettes. The report also concludes that the marketing of these products as delivering less tar and reducing risk is "deceptive" and smokers' choice of these products as an alternative to quitting makes this deception an "urgent public health issue."

This special report from the Campaign for Tobacco-Free Kids contains links to the actual NCI monograph and a joint statement from various public health organizations.
http://tobaccofreekids.org/reports/lowtar/

Consumers expect the term “light” to mean something: by law, “light” beer must be below a certain percentage in alcohol, and “light” margarine must have appreciably fewer calories. In the case of cigarettes, however, the term “light” is completely unregulated. Companies use the term as they see fit to refer loosely to how much ‘tar’ a machine is exposed to when it smokes the cigarette. Unfortunately, human beings do not smoke like machines, and smokers are routinely exposed to far more ‘tar’ than machine smokers — particularly when they are smoking light cigarettes.

Physicians for a Smoke-free Canada and the Non-Smokers' Rights Association give more details, including references to once-secret tobacco company documents.
http://www.nsra-adnf.ca/english/lights/

A Marketplace video "Light Cigarettes", which aired in 1980, tells a story as true today as 20 years ago. Read the article, and watch the video.
http://www.cbc.ca/consumers/market/mp30/light_cigarettes.html#