PURPOSE: To compare the clinical therapeutic efficacy of finasteride and dutasteride as 5-alpha reductase inhibitor (5-ARI) in the medical treatment of benign prostate hyperplasia. MATERIALS AND METHODS: From July 2007 to July 2010, 354 benign prostatic hyperplasia patients with combination medication : alpha blocker plus 5-ARI were enrolled. These patients were classified into a finasteride medication group (F group) and dutasteride medication group (D group) retrospectively. We initially measured the total prostate volume (TPV), prostate specific antigen (PSA), International Prostate Symptom Score (IPSS), quality of life score (QoL), maximal flow rate (Qmax), and post-void residual urine (PVR). After at least twelve months of medication, we rechecked these clinical parameters and during medication, side effects related to medication were also recorded. RESULTS: The F group (n=129) and D group (n=225) showed no differences in baseline characteristics for age, TPV, IPSS, QoL scores, or PSA. After medication, decreases in TPV were relatively higher in the D group than the F group (28.2% vs 20.5%). In addition, the decrease in PSA (43.6% vs 39.2%) and IPSS score (4.6 vs 3.5) were also higher in the D group. There were no significant differences in QoL score, Qmax, PVR change, or side effects between the two groups. CONCLUSIONS: Dutasteride showed greater efficacy in reduction of TPV and PSA and in symptomatic improvement by IPSS score than finasteride. More large scale studies about the differences on clinical efficacy of finasteride and dutasteride are needed.