Full disclosure of medical diagnosis to cancer patients in Japan remains controversial. Some physicians in Japan believe that full disclosure may affect the outcome of treatment, create stress and psychiatric problems, or lead to suicide. Although the trend toward full disclosure is increasing in Japan, approximately 70% of current cancer patients are still not fully informed of their condition. In this study, the authors examined the psychiatric status and effects of full disclosure among 100 otolaryngology patients at Tokai University Hospital (50 with benign diseases, 50 with malignancy) using major depression and adjustment disorders criteria of the DSM-III-R Structured Clinical Interview (SCID). This demonstrated that 15 of 50 (30%) patients with benign diseases and 23 of 50 (46%) patients with malignant diseases met the criteria for depression and adjustment disorder; 29 of the 50 patients (58%) with malignant cancer were not informed of their true condition, according to the wishes of their families (21 were fully informed). The prevalence rate of psychiatric disorders was 42.9% among the informed group and 48.3% among the uninformed group. These findings suggest that concealing the true diagnosis was not related to the presence of psychiatric disorders in Japanese cancer patients.