The CDT is a useful screening instrument for assessing cognition. The aim of this study is to identify which structural change of the brain is related with the CDT performance. Eighty-four patients with memory impairment were enrolled. The Korean versions of the mini-mental state examination (K-MMSE) and the modified mini-mental state (3MS) test, and the Seoul Neuropsychological Screening Battery (SNSB) were given to every subject. Four CDT scoring methods were used. The cerebral white matter hyperintensity (WMH), cortical atrophy (CA), ventricular enlargement (VE), and medial temporal lobe atrophy (MTA) were rated by two neurologists who were kept "blind" to the clinical information. The cognitive and executive functions were significantly correlated with the CDT performance. The degree of WMH and MTA showed an inverse relation with the CDT performance. The periventricular WMH (PVH) contributed more to impairment of CDT, than that of the deep WMH (DWMH). This study suggests that a combination of executive dysfunction via the frontal-subcortical disruption due to the PVH and memory impairment due to the MTA might be responsible for further worsening on the CDT.