Aim: The aim of this study was to evaluate the oxidative stress status and antioxidant capacity in patients with localized prostate cancer (PCa) and benign prostatic hyperplasia (BPH). Material and Method: The prospective study consisting 24 men with PCa and 36 men with BPH. PCa or BPH were diagnosed histologically. Blood samples were obtained following an overnight fasting state. We evaluated and compared the total oxidant status (TOS), total antioxidant capacity (TAC), paraoxonase1 (PON1), arylesterase and total thiol levels of patients with PCa and BPH. Results: The mean age of BPH group was 67 +/- 12 years and PCa group was 63 +/- 8 years (p>0.05). No statistically significant differences were detected between the groups in terms of oxidative stress parameters and antioxidant capacity measured in the serum of patients including PON1, TOS, TAC, arylesterase and thiols levels (p>0.05 for all parameters). Discussion: Our results demonstrated that evaluation of these parameters in the serum of BPH and localized PCa patients may not be used as a marker to discriminate between these diseases.