text: Researchers continue to study the causes of lung cancer and to search for ways to prevent  it. But, about 90% of all lung cancer deaths among women are from smoking. Even though \nwe know its effects are harmful, 1 out of every 5 women in the U.S. still smokes. We already  know that the best way to prevent lung cancer is to quit (or never start) smoking. The soone r a person quits smoking the better. Even if you have been smoking for many years, it's never  too late to benefit from quitting