Impulsivity is a dimensional construct which is crucial in defining the overt symptomatology of several psychopathological disorders. From a neuropsychological perspective, motor inhibition ability is conceptualized as an executive function involved in self-regulation; its impairment may cause the execution of impulsive behaviours. Aim of this paper is to review the main studies that investigated this ability in four clinical groups: Obsessive-compulsive disorder, trichotillomania, pathological gambling,substance use disorders. To date, existing behavioural data do not allow to support the presence of inhibitory problems in these disorders; nonetheless, neuroimaging studies have found several abnormalities in frontal lobe's activity.