In the past years, obsessive-compulsive disorder has mainly been described in adults. However, recent epidemiological data has shown that 2 to 3% of the school-age population has OCD symptoms in the clinical range of severity. Despite these findings, this disorder remains still unknown and under recognized by child's clinicians--general practitioners, paediatricians or child and adolescent psychiatrists. This may contribute to the particularly damaging delay occurring in diagnosis and specific treatment of childhood onset OCD. Therefore, this article intends to review the main clinical signs likely to allow an early detection of OCD in child as well as the principal therapeutic methods currently in progress.