Cornerstone Developmental Psychology has two convenient locations on Long Island, New York. We specialize in individual and family therapy, and specialized diagnostic and psycho-educational evaluations. We also offer comprehensive evaluations for OPWDD eligibility and legal guardianship. Our Licensed clinical and school psychologists offer evidence based treatment for children, adolescents, adults, couples, and families in both Nassau and Suffolk County. We offer flexible appointment times with day and evening hours for therapy and assessment.