The antiradical property of hot water extract from dried radish (DR) or dried radish roasted with pressure (DRRP) was investigated in vitro and in LLC-PK1 cell system. The contents of total free amino acid and reducing sugar in DR were decreased by 72.86% and 3.17%, respectively, after pressurized roasting. In vitro test, IC50 for DR and DRRP for DPPH radical scavenging activity were 646.70 and 135.45 μg/mL, 896.10 and 566.98 μg/mL for superoxide anion radical, and 722.26 and 531.84 μg/mL for hydroxy radical, respectively. The radical scavenging effects of DRRP was significantly greater than those for DR (p<0.001). These radical scavenging effects of DR and DRRP were confirmed in LLC-PK1 at which oxidative stresses were induced by superoxide, nitric oxide and peroxynitrite generated in the treatment of pyrogallol, SNP, and SIN-1, respectively. Cell viability was increased in the presence of DR or DRRP, dose dependently (p<0.05), and TBARS formation was decreased. The protective effects of DRRP against oxidative damage in LLC-PK1 were greater than those of DR at the same concentration tested (p<0.05). This superior antiradical activity of DRRP might be due to the products produced during the pressurized roasting in addition to the anti oxidative compounds originally present in the radish. 5-hydroxyl methyl furfural (5-HMF) known as an intermediate product of the maillard reaction was detected in DRRP (0.57 mg/g), but not from DR. In conclusion, daily consumption of DRRP may prevent oxidative damage by retarding oxidative stress.