OCSDs are characterized by difficulties suppressing repetitive behaviors that are suggesting underlying impairment in inhibitory control. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, OCD has been reclassified within a new chapter of obsessive-compulsive and related disorders that includes trichotillomania and skin picking, in which impulsive features are core characteristics. In some aspects, both impulsive and compulsive disorders show similar clinical features, such as difficulties in delaying or inhibiting repetitive behaviors. Compulsive and impulsive disorders are often comorbid and influence each other’s development. A number of studies reported high prevalence of impulse control disorders in OCD and high prevalence of OCD in ICDs. In addition, the impulsiveness in OCD seems to have various significant clinical implications. Comorbid ICDs in patients with OCD are associated with poor clinical characteristics, such as early age at onset, great number and severity of symptoms, poor insight, insidious onset, impaired functioning, and poor treatment response seen at longterm follow-up. OCD subjects with higher impulsivity show higher learning problems, low frustration tolerance, poor interpersonal relationships, attention-seeking behavior in childhood, higher neuroticism, and a higher incidence of somatic symptoms. Additionally, based on neuroimaging and lesion studies, one of the major areas involving impulsivity is the ventral striatal loop, which is a target area of deep brain stimulation to improve obsessive-compulsive symptoms in refractory. Despite this substantial evidence suggesting the importance of impulsivity in OCD, there have been few studies on this relationship and these have mainly used self-rating measures. Impulsivity is not a unidimensional construct and it has been suggested that there are several distinct facets of impulsivity, including behavioral disinhibition, impulsive decision making, and unduly risk taking. Behavioral disinhibition is defined as an active process that involves suppression of a prepotent response that has been actively investigated by using the stop signal task. Impulsive decision making is characterized by making choices for BAY 73-4506 755037-03-7 smaller immediate rewards rather than waiting for larger delayed rewards. The delay discounting task is a well-known behavioral task that measures delay discounting, which refers to the devaluing of a reward due to its location in the future; in other words, DDT assesses the tendency to discount future rewards. Risky decision making is the tendency to engage in behaviors with some potential for danger or harm while also providing an opportunity to obtain some form of reward. The balloon analogue risk task is a computerized measure that assesses the tendency to engage in simulated risk taking behavior in a context in which unduly risky behavior results in poor outcomes. Considering the multidimensionality of impulsivity, it would be fruitful to simultaneously evaluate the various dimensions of impulsivity as well as by using a self-rating measure.