Smoking cessation is a difficult process for many people, and the use of bupropion has been found to be an effective aid in helping individuals quit smoking. Bupropion is a medication that works by blocking the reuptake of dopamine and norepinephrine, two neurotransmitters involved in reward pathways. It also increases levels of serotonin, which can help reduce cravings for nicotine. Bupropion is used to treat depression, bipolar disorder, and attention deficit hyperactivity disorder (ADHD). It is also used to help people stop smoking. Side effects include drowsiness, anxiety, difficulty falling asleep, dry mouth, dizziness, stomach pain, uncontrollable shaking, excessive sweating, and ringing in the ears. More serious side effects include changes in behavior, hostility, agitation, depressed mood, and suicidal thoughts. Despite the efficacy of bupropion for smoking cessation, smokers exhibit variability in treatment outcomes. Smokers with a decreased activity variant of CYP2B6 reported greater increases in cravings for cigarettes following the target quit date and had higher relapse rates. COMT haplotypes at rs737865 and rs165599 may predict a favorable outcome for bupropion treatment for smoking cessation. European-American smokers with a G allele at both SNPs may not benefit from bupropion treatment. Recent research has identified genetic variants associated with bupropion’s effectiveness as a smoking cessation aid. The first variant studied was rs3211371, located on chromosome 15q25-26 near the gene CHRNA5-CHRNA3-CHRNB4 (also known as “the nicotine receptor cluster”). This variant has been linked to an increased risk of developing nicotine dependence and decreased response to bupropion treatment for smoking cessation. Individuals who carry this variant may need higher doses or longer courses of treatment than those without it in order to achieve successful quitting outcomes. Another variant studied was rs165599, located on chromosome 17q12 near the gene CYP2B6 (which encodes an enzyme involved in metabolizing drugs such as bupropion). This variant has been linked to reduced metabolism of bupropion and improved response rates when using it for smoking cessation compared with non-carriers. Individuals carrying this variant may require lower doses or shorter courses of treatment than those without it in order to achieve successful quitting outcomes.