Objective: The aim of this study was to investigate the effect of prolactin levels, duration of disease, accompanying metabolic syndrome, use of mood stabilizer drugs, smoking and exercise on bone mineral density (BMD) in patients treated with antipsychotics. Methods: Fifty-six patients who had been diagnosed with schizophrenia, forty-one patients who had been diagnosed with schizoaffective disorder and thirty three patients who had been diagnosed with bipolar disorders were included the study. BMD was measured at the lumbar spine and femoral sites using dual energy x-ray absorptiometry (DEXA). Arterial blood pressure, waist circumference, fasting glucose, HDL cholesterol and triglyceride levels of the patients were measured for diagnosis of metabolic syndrome. The age, weight, height, smoking habits, regular physical exercise, additional mood stabilizer drugs administered and blood prolactin levels were recorded. Results: Results of 73 patients were osteopenia or osteoporosis. There was no statistically significant relationship between BMD and plasma prolactin level, using additional mood stabilizer drugs, dose of antipsychotic drugs and metabolic syndrome. There was negative correlation between duration of illness, duration of antipsychotic drug use and BMD of the femoral neck. There was negative correlation between duration of smoking and BMD of femoral intertrochanteric region. Lumbar BMD was significantly higher in patients exercising regularly than those of patients without regular physical exercise. Conclusion: Due to a sedantary lifestyle, pro-longed use of antipsychotic drugs and smoking risk of osteoporosis increases in patients with schizophrenia, schizo-affective disorder and bipolar disorder. BMD of these patients should be followed-up with regular intervals. (Ana-tolian Journal of Psychiatry 2019; 20(x):xx-xx) [Anadolu Psikiyatri Derg 2019; 20(2.000): 182-188]