Obsessive-compulsive disorder (OCD) has been categorized separately from other anxiety disorders in DSM-5, and is currently conceptualized as a disorder that is characterized by having preoccupations (obsessions) and/or repetitive behaviors (compulsions). Disorders with phenomenological and psychopathological features similar to those of OCD also consist of obsessive-compulsive and related disorders (OCRD) that have been newly introduced into DSM-5. Some OCRDs such as body dysmorphic disorder and hoarding disorder are characterized by preoccupations and repetitive behaviors or mental acts in response to the preoccupation, while others are primarily characterized by recurrent body-focused repetitive behaviors (e.g. hair pulling and skin picking) and repeated attempts to decrease or stop the behaviors. However, OCD and anxiety disorders often share core clinical features such as elevated anxiety, fear conditioning, avoidant behaviors, and a higher prevalence of comorbid major depression as well as effective treatment strategies such as SSRI or CBT. Thus, the relationship between OCD and anxiety disorders is very complex and may be attributed to the heterogeneity of OCD (e.g. cognitive or motoric OCD) and the broader range of its concept, which even includes continuity with autism spectrum disorders or impulsive or addictive disorders. Therefore, further studies are needed in order to confirm the validity and clinical utility of the current diagnostic concept of OCD and determine the future direction of OCD.