Introduction: Most cognitive screening instruments are tailored to detect symptoms of cortical dysfunction in the elderly. Therefore, subcortical cognitive dysfunction may be missed using these tests. The aim of this study was to validate the Human Immunodeficiency Virus (HIV) Dementia Scale (HDS), a screening test developed to detect subcortical cognitive dysfunction in young HIV-infected patients, in a group of elderly patients with subcortical cognitive impairment (SCI) caused by subcortical ischaemic vascular disease (SIVD) or a normal pressure hydrocephalus (NPH). Materials and Methods:53patients with SCI caused by SIVD or an NPH and 54 age-matched control subjects without cognitive impairment were included. All subjects underwent the HDS and the Mini-Mental State Examination (MMSE). A neuropsychological examination was used as the best reference test for the diagnosis of SCI. Results: The mean HDS score (maximum 16) was 5.1 ± 3.5 in the SCI patients and 13.0 ± 2.4 in the controls (p < 0.0001). The mean MMSE score (maximum 30) was 26.5 ± 3.1 in the SCI group and 28.6 ± 1.4 in the controls (p < 0.0001). Among subjects who had an MMSE score of more than 26 points, SCI patients (n = 35) also scored significantly lower on the HDS than controls (n = 50), mean scores being 6.2 ± 3.4 and 13.0 ± 2.4, respectively (p < 0.0001). A receiver-operating characteristics curve was used to detect the optimal sensitivity and specificity of the HDS. A cut-off score of 9 yielded 91% sensitivity (95% CI: 79–97) and 96% specificity (95% CI: 87–99). With this cut-off score, the positive predictive value was 96% (95% CI: 86–99) and the negative predictive value was 91% (95% CI: 81–97). Conclusions: These results suggest that the HDS is able to detect SCI in an elderly population with SIVD or NPH and a normal MMSE score, and warrant its further development as a screening tool for SCI.