Attention deficit hyperactivity disorder (ADHD) is characterized by inattention, impulsivity, and hyperactivity that are frequently treated with stimulant medications such as Ritalin. Many people with ADHD smoke. The smoking prevalence rates are estimated to be 40% in adults with ADHD compared to 20% in the general population. People with ADHD have also more difficulty to quit smoking. Only 29% of smokers with ADHD quit smoking compared to 48.5% of smokers in the general population. Nicotine is a stimulant, which may have properties similar to stimulant medications (e.g., Ritalin) used to treat ADHD. Nicotine may increase attention and reduce hyperactivity and impulsivity and, thus, may regulate behavior in individuals with ADHD. Alleviating the symptoms of ADHD and increasing cardiovascular activity through smoking may mimic the effects of stimulant medications and can be a form of self-medication.