Femoral neck fractures are the second cause of hospitalization in elderly patients. Nowadays it is still not clear whether surgical treatment may provide better clinical outcome than conservative treatment in patients affected by mental disorders, such as senile dementia. The aim of this study was to retrospectively assess mortality and clinical and functional outcome after hemi arthroplasty operation following intracapsular neck fractures in patients with senile dementia. Between 2008 and 2014, 819 patients were treated at our Orthopaedic Institute for neck fracture of the femur (mean age: 83.8 years old). Eighty-four of these showed clear signs of cognitive impairment at time of admission in the Emergency Department. Mental state of patients was assessed in all cases, as routine, at the Emergency Room with the Short Portable Mental Status Questionnaire (Sh-MMT) and the Mini Mental State Examination (MMSE). Patients were divided in two groups depending whether they were surgically treated with hemiarthroplasty (Group B, 46 patients; 35 females, 11 males; mean age: 88.5 y.o.) or conservatively treated (Group C, 38 patients; 28 females, 10 males; mean age: 79.5 y.o.). These two groups were compared with a matched case-control group of patients surgically treated with no mental disorders (Group A, 40 patients; 34 females, 6 males; mean age: 81.5 y.o.) Incidence of mortality, systemic or local complications and functional clinical outcomes were evaluated with the ADL score and the Barthel index. Mortality rate was 35% (14 patients) for Group A, 50% (21 patients) for Group B and 95% (22 patients) for Group C. Paired t-test, with significance rate set at 0.05, showed significant higher mortality rate in Group A compared to both Group B ( Activity daily living scale and Barthel Index results showed higher results in Group B than Group C both in terms of recovery of walking ability and daily living (hairdressing, wearing clothes, eating).