Additional Study Information: This research study aims to identify brain differences that underlie OCD in children by assessing changes in the brain after treatment with cognitive behavioral therapy (CBT). This study includes a thorough diagnostic evaluation, a full course of CBT (12 sessions), and fMRI scans before and after treatment. All study procedures, including the evaluation, treatment, and fMRI scans are at no cost. In addition, your child will receive compensation up to $350 in the form of a gift card for participating in this study.