ABSTRACT Background: Our study investigates whether Native Thiol, Total Thiol and disulphide levels measured in serum of patients with prostate cancer and prostatitis and of healthy subjects, have any role in differential diagnosis. Materials and Methods: Patients followed up for histopathologically verified diagnosis of prostate cancer and prostatitis in 2016-2017 at the Medicalpark Gaziantep Hospital Urology Clinic were included in the study. Native Thiol (NT), Total Thiol (TT), Dynamic Disulphide (DD) levels in serum were measured by a novel automated method. Results: NT, TT, DD, NT / TT ratios, DD / TT ratio and DD / NT ratio were measured as 118.4 ± 36.8μmoL / L, 150.3 ± 45.3μmoL / L, 15.9 ± 7μmoL / L, 78.8 ± 7μmoL / L, 10.5 ± 3.5μmoL / L, 13.8 ± 5.8μmoL / L respectively in patients with prostate cancer; as 116.4 ± 40.5μmoL / L, 147.5 ± 50.1μmoL / L, 15.5 ± 8.7μmoL / L, 79.7 ± 9μmoL / L, 10.1 ± 4.5μmoL / L, 13.5 ± 7.2μmoL / L in patients with prostatitis and as 144.1 ± 21.2μmoL / L, 191 ± 32.3μmoL / L, 23.4 ± 10.1μmoL / L, 76.1 ± 98.3μmoL / L, 11.9 ± 4.1μmoL / L, 16.4 ± 6.9μmoL / L in healthy subjects. Significant difference was detected between groups of NT, TT and DD levels (p = 0.008, p = 0.001, p = 0.002). No significant difference was detected in terms of the NT / TT, DD / TT and DD / NT rates (p = 0.222, p = 0.222, p = 0.222). Conclusions: Serum NT, TT, DD levels in patients with prostatitis and prostate cancer were found significantly lower compared to the control group. This indicates that just as inflammation, prostate cancer also increases oxidative stress on tissues.