Obsessive-Compulsive Disorder (OCD) is characterized by obsessions, intrusive, unwanted thoughts, and compulsions, repetitive acts or behaviours performed in an inflexible, ritualistic way. OCD is ego-dystonic in nature as patients are generally able to recognize their compulsive behaviours and thoughts as disproportionate, excessive, and maladaptive. Traditionally, cognitive theories posited dysfunctional beliefs as a major driver of OCD symptoms. More recently, however, experimental evidence showing a tendency for OCD patients to display habitual behaviour at the expense of goal-directed actions has suggested that OCD is a disorder of habitual control. In this talk, I will present data gathered from independent behavioural paradigms and computational modelling studies that tested the hypothesis that autonomous, habit-like behaviours are detached from intact, explicitly reported knowledge of higher order environmental contingencies. Finally, I will also present data from fMRI studies showing that such inflexible behaviours are associated with dysfunctional organization of fronto-striatal circuits.