Insurance companies rate the insured based on various risk factors. When someone is a smoker it increases the risk borne by the insurance company since statistically, smokers generally will not live as long as non-smokers. Smoker ratings will increase the premium of a life insurance policy. Generally, insurance carriers will consider you a non-smoker if you have not smoked within the past year.
A word of caution; if you lie on an application about being a non-smoker when in fact you are a smoker, in the event of your death if the insurance company can prove that you intentionally lied on the application when applied for, your beneficiary may not receive the full death benefit – they may only receive the premiums you paid into the policy. Nicotine can be detected by numerous tests and is routinely tested for by insurance companies.