Background: Wilson's disease (WD) is a rare autosomal-recessive, inherited disorder caused by a mutation in the copper-transporting gene ATP7B affecting the liver and nervous system. About 30% of patients with WD may initially present with psychiatric symptoms, and diagnosis can be difficult to establish. The objectives of the present preliminary study were [1] to evaluate the relevance of serum copper (Cu) and ceruloplasmin (Cp) measures in hospitalized patients with psychiatric disorders; and [2] to identify possible mutations in the ATP7B gene in patients with abnormal biological copper profile. Methods: All psychiatric patients who participated in this study were hospitalized in Saint-Jean de Dieu Hospital (Lyon, France). Cp was measured by immunoturbidimetry and serum Cu by inductively coupled plasma-optical emission spectrometry. When Cp and serum Cu levels were inferior to, respectively, 0.18 g/L and 0.88 mg/L in combination with atypical psychiatric presentations, complete clinical examinations were performed by multidisciplinary physicians specialized in WD. In addition, mutation detection in the ATP7B gene was performed. Results: A total of 269 patients completed the study. (1) 51 cases (19%) showed both decreased Cp and Cu concentrations. (2) Molecular genetic tests were performed in 29 patients, and one ATP7B mutation (heterozygous state) was found in four patients. We identified three different missense mutations: p.His1069Gln, c.3207C>A (exon 14), p.Pro1379Ser, c.4135C>T (exon 21) and p.Thr1434Met, c.4301C>T (exon 21). No pathogenic mutation on either ATP7B allele was detected. Conclusion: Results of Cp and/or serum Cu concentrations below the normal limits are common in patients with psychiatric disorders and nonrelevant and/or informative for the WD diagnosis. WD diagnosis is based on a combination of clinical and biological arguments. Psychiatric patients with suspicion of WD should be evaluated in a reference center.