The incidence of depression in patients with brain tumors varies in the range from 10% to 80%. Both anatomic and physiological perturbations in the brain are likely involved in the associations between depression and brain tumors. Tumor treatments are also associated with depression. 115-adult-brain-tumor-patients were examined at the Department of Neurosurgery, Clinical Hospital Center Zemun, by using a clinical Hamilton Depression Scale (HADS). The level of depression and symptoms was studied before tumor operation as well as at three months after operation. Before tumor operation 16% of the patients had depression according to Hamilton Depression Scale (HADS), while 10% had depression at three months after operation. This research illustrates the need for a prompt neuroimaging of the brain when patients present any atypical psychiatric symptoms, late onset of (>50 years old) first depressive episode or fast changes in the mental state. Better understanding of the relationships between brain tumors and depression should lead to improvement in patient care.