Objective: Attention deficit hyperactivity disorder (ADHD) and bipolar disorder are frequently comorbid diagnoses. Aim of this study was to compare the neurological soft signs in patients with bipolar disorder and in patients with comorbid ADHD to those in control subjects. This study helps us to understand the impact of ADHD on the soft neurological signs in bipolar disorder in adults.Methods: Sixty euthymic patients diagnosed with bipolar I disorder and 33 healthy control subjects were enrolled in the study. The Wender Utah Rating Scale, Adult ADHD Rating Scale and The Structured Clinical Interview for DSM-IV Disorders were administered to the participants. The subjects were classified into three study groups, namely, bipolar patients with comorbid ADHD (n=13), bipolar patients without comorbid ADHD (n=47) and controls. We performed the Neurological Evaluation Scale in the three groups. Results: Comorbid ADHD group showed poor performance on complex motor tasks such as fist-ring test and fist-edge–palm test, while bipolar group showed poor performance on Ozeretski test. Comorbid ADHD patients performed poorly on graphestesia, stereognosis and primitive reflexes. Conclusion: Abnormalities of repetitive motor performance and primitive reflexes observed in comorbid ADHD patients support the hypothesis that ADHD involves a deficit in fronto–striatal-thalamic neurocircuits. In contrast, impaired sequential motor performance in BP subjects shows deficits in dorsolateral prefrontal cortex. These results show that the pathophysiology of bipolar disorder and ADHD may be related to different areas, and comorbid ADHD may increase the severity of the soft neurological signs. (Archives of Neuropsychiatry 2011; 48: 107-13)