We examined clinical presentations, neuropsychological findings, and perfusion patterns of 99mTc-ethyl cysteinate dimer (ECD) single photon emission computed tomography (SPECT) in patients with early stage dementia with Lewy bodies (DLB) (n = 17) and Parkinson’s disease (PD) (n = 16), with age-matched healthy controls (n = 10). Seven paired regions of interest (ROIs) were drawn manually including inferior frontal, temporal, parietal, occipital, parieto-occipital junction, striatum and thalamus for semiquantitative measurement. Neuropsychological tests were applied for clinical correlation. The SPECT results showed significant hypoperfusion in DLB group in frontal, parietal, thalamus, temporal ROIs compared with controls (P < 0.01) whilst signals in temporal areas was significantly reduced compared with PD group (P < 0.05). Neuropsychological tests showed that DLB patients had deficits in mental manipulation, short-term memory, abstract thinking, drawing and semantic verbal fluencies (P < 0.05, compared with control). In addition, DLB group had lower scores than those with PD in mental manipulation, drawing and semantic verbal fluency (P < 0.05). Our study showed that even in early stages of DLB, neuropsychological and perfusion patterns were evident and may be different from PD group, despite they shared certain similarities both in neuropsychological and image findings compared with age-matched controls.