The primary purpose of this study is to learn whether personalized assessment of obsessive-compulsive disorder (OCD) symptoms in childhood OCD using mobile health technology are feasible and acceptable for youth and parents. The investigators will also examine whether personalized cognitive-behavioral therapy (CBT) that is informed by personalized OCD assessments yields better clinical outcomes when compared to standard CBT for youth with OCD

Inclusion Criteria:

1. be 8-17 years of age;
2. meet diagnostic criteria for a primary diagnosis of OCD on a structured clinical interview;
3. have moderate OCD severity as evidenced by a CY-BOCS total score of ≥16;
4. medication free and/or on a stable dose of medication 8 weeks prior to study participation;
5. be English speaking.

Exclusion Criteria:

1. the presence of psychotic disorder, bipolar disorder, or autism spectrum disorders;
2. significant suicidal ideation that warrants medical intervention;
3. concurrent psychotherapy for OCD;
4. inability to complete scales, or attend visits.