Attention-deficit hyperactivity disorder (ADHD) is a common psychiatric disorder in children which manifests with hyperactivity, impulsivity, and/or inattention. Several drugs are used in treatment of ADHD. Stimulants, atomoxetine, anti-depressants, and bupropion are common medications used in the treatment of ADHD. Stimulants are widely used as the first line treatment in children with ADHD. Their mechanism of action is the release of dopamine and norepinephrine in central nervous system. Methylphenidate is the most common stimulant used for the treatment of ADHD. Methylphenidate significantly reduces ADHD symptoms in children both at home and school and improves their social skills. Methylphenidate is safe in healthy children and has shown to have no cardiac side effects in these patients. Other medications include: Atomoxetine, Amphetamines, Clonidine, Melatonin, and anti-depressants. Effects, side effects, and mechanism of action these drugs have been discussed in this paper.