Context: Data regarding the presence, extent, and reversibility of psychological and cognitive features of primary hyperparathyroidism (PHPT) are conflicting. Objective: This study evaluated psychological symptoms and cognitive function in PHPT. Design: This is a case-control study in which symptoms and their improvement 6 months after surgical cure of PHPT were assessed. Settings: The study was conducted in a university hospital metabolic bone disease unit and endocrine surgery practice. Participants: Thirty-nine postmenopausal women with PHPT and 89 postmenopausal controls without PHPT participated in the study. Intervention: Participants with PHPT underwent parathyroidectomy. Outcome Measures: Measurements used in the study were: Beck Depression Inventory (BDI); State-Trait Anxiety Inventory, Form Y (STAI-Y); North American Adult Reading Test (NAART); Wechsler Memory Scale Logical Memory Test, Russell revision (LM); Buschke Selective Reminding Test (SRT); Rey Visual Design Learning Test (RVDLT); Booklet Category Test, Victoria revision (BCT); Rosen Target Detection Test (RTD); Wechsler Adult Intelligence Scale-Revised Digit Symbol Subtest (DSy); Wechsler Adult Intelligence Scale Digit Span Subtest (DSpan). Results: At baseline, women with PHPT had significantly higher symptom scores for depression and anxiety than controls and worse performance on tests of verbal memory (LM and SRT) and nonverbal abstraction (BCT). Depressive symptoms, nonverbal abstraction, and some aspects of verbal memory (LM) improved after parathyroidectomy to the extent that scores in these domains were no longer different from controls. Baseline differences and postoperative improvement in cognitive measures were independent of anxiety and depressive symptoms and were not linearly associated with serum levels of calcium or PTH. Conclusions: Mild PHPT is associated with cognitive features affecting verbal memory and nonverbal abstraction that improve after parathyroidectomy. Copyright © 2009 by The Endocrine Society.