Attention-deficit Hyperactivity Disorder is one of the most common childhood mental health disorders, affecting about 5.6% of the population worldwide. Several studies have specifically shown a high prevalence of comorbid mood disorders, such as depression and bipolar disorder (BD), in those diagnosed with ADHD. Several common symptoms of ADHD are also found in BD, which are characterized by alternating periods of euthymia and mood disturbances. The inattention and impulsivity of ADHD can be seen in manic and hypomanic episodes of BD. Over the past decade, there has been an increased interest in research between the correlation of ADHD and pediatric bipolar disorder (PBD) in children. Some experts hypothesize that more children are comorbidly diagnosed with ADHD and PBD because of how many clinicians treat children with ADHD. Other factors, which may affect the dual diagnoses of ADHD and PBD, are overlapping diagnostic criteria for the two disorders, the inevitable biases seen when one disorder is diagnosed without the other, and related risk factors leading to prodromal relationships. By examining clinical trials, a better understanding of whether ADHD and PBD have a stepwise progression or if other factors influence these comorbidities, such as blurred lines of diagnostic criteria. Those with ADHD are also at an increased risk of impairment at work and in social settings. This manuscript explores both progression of this disease and its clinical connections to other disorders.