Nearly all cases of first time tobacco use take place before a person finishes high school, according to the American Cancer Society (ACS). The younger people are when they begin to smoke, the more likely they will become adult smokers. Almost three out of four regular smokers in high school have already tried and failed to quit, the ACS says. Smoking at a young age can set up a person for smoking-related illnesses, such as heart disease and lung problems, earlier in life.