Objective To study the comorbidity of somatic dis e ases and its significance among patients of psychiatric department of geriatrics . Methods The data about psychiatric diagnoses, co-existing so matic diseases and curative efficacy of mental diseases were investigated among 198 patients. Results 91.4% of patients co-existed somatic diseases, and the m ean of sort of somatic diseases among each patient was 1.65. Somatic diseases ma inly included pulmonary infection, cerebral vascular disease (CVD), hyper tension, heart disease, diabetes mellitus (DM) and chronic obstructed pulmonary disease (COPD), etc. By logistic regression, it was found that Alzheimer's disea se (AD), the numbers of somatic diseases and co-existing CVD w ere disadvantageous factors of the curative efficacy of mental diseases. Conc lusions The comorbidity of somatic diseases is common among patients of psychiatric department of geriatrics and it affects treatments and curative eff icacy of mental diseases. Furthermore, the comorbidity influences the clinical m odel of psychiatric department of geriatrics.