Introduction: Oral diseases in psychiatric patients are usually a result of bad oral hygiene and psychopharmaceutical side-effects. Objective: The aim of this study was to detect the most prevalent oral lesions in patients hospitalized in a psychiatric institution in Caracas, Venezuela with the confirmed diagnosis of psychiatric illness. Methods: A transversal study consisted of 65 hospitalized patients with psychiatric disorders out of whom 50 were males and 15 females. Patients were aged from 19 to 80 years, mean age 50.2 years. Data on oral lesions were obtained within history and clinical examination of the oral cavity. Other medical data were collected from medical documentation. Statistical analysis was performed by SPSS version 17.0. Results: 56.92% of patients had caries in at least one tooth, 29.23% presented gingivitis and 56.92% periodontal disease. In relation to Temporomandibular joint, 36.92% presented articular sounds and 10.76% muscular pain. Between the most prevalent parafunctional habits were found cigarette habit, bruxism, onychophagia and cheek bite. Conclusion: Results imply that psychiatric patients are more frequently involved with oral lesions than healthy persons. It is necessary to organize specific preventive and educational oral health programmes with these patients, in a multidisciplinary group.