Juvenile obsessive-compulsive disorder (OCD) has been hypothesized to be different from adult-onset OCD suggesting that juvenile OCD may be a developmental subtype of the disorder. There is some evidence that juvenile OCD may be phenotypically different from juvenile-onset adult OCD. This study examines the phenotypic characteristics of juvenile OCD (current age < or = 18 years, n = 39), juvenile-onset adult OCD (onset < or = 18 years, current age >18 years, n = 87) and adult-onset OCD (onset > 18 years, n = 105). Qualified psychiatrists expert in evaluating OCD subjects conducted clinical and structured interviews. In the multinomial logistic regression analysis, controlling for chronological age and gender, the juvenile OCD was associated with male preponderance, elevated rates of certain obsessive-compulsive symptoms, attention-deficit hyperactivity disorder, chronic tics, body dysmorphic disorder and major depression. In addition, juvenile-onset adult OCD differed from juvenile OCD by having later age-at-onset and low rate of ADHD. The juvenile-onset adult OCD was positively associated with social phobia and chronic tics compared to adult-onset OCD. The juvenile OCD appears to be different from both juvenile-onset adult OCD and adult-onset OCD supporting previous observations that juvenile OCD could be a developmental subtype of the disorder.