Examples of compulsions include counting, repeating words or actions (for example, checking locks or hand washing), arranging things according to rigid rules, and praying. These behaviors are done for the purpose of preventing or decreasing anxiety or preventing an unrealistic dreaded event. An example of an unrealistic dreaded event is becoming ill if hands are washed less than once every half hour. The symptoms of OCD either significantly interfere with the sufferer's daily routine or functioning (for example, causing insomnia or difficulty concentrating at work), cause significant stress, or take up a lot of time.

In contrast to symptoms of OCD in adults, those in children may include a lack of insight that their obsessions or compulsions are a problem. Symptoms in children may also include tantrums when the child's ability to engage in compulsions is prevented. Symptoms of OCD in teenagers often involve physical (somatic) complaints. While the severity of OCD symptoms can change in their level of severity, the kind of symptoms tends to change little in adults compared to children and teens.