HOLLYWOOD, Fla. -

Barbaree King began smoking when she was a teenager. She struggled for years to quit.

"At some time, I had quit for a couple of years and in a moment of weakness, I said, 'I'll just have one' and I did," she said.

King wondered why smoking cessation aids never seemed to help her, but researchers may now have an answer.

The U.S. National Institute on Drug Abuse found several genetic variations that may play a role in whether people will respond well to nicotine replacement therapy and the smoking cessation drug Bupropion. Researchers found 41 genetic variants linked to smokers who were able to quit using nicotine replacement therapy, including patches and gum, and 26 genes that could help people successfully quit with Bupropion.

"Some people will be able to quit without the medication. Some people are going to have a really tough time," said Dr. Mark Block, a lung specialist with Memorial Health Care System.

Block said the research may lead to more tailored treatment approaches.

"You don't want to give medication to people who aren't going to benefit from it and by the same token, you don't want to withhold it from people who are really going to benefit, so it's a nice way to target therapy based on genetics," he said.