To investigate the relationship of cyclooxygenase-2 (COX-2) polymorphisms [COX-2 -765 G/C (rs 20417)] and susceptibility to hepatitis B-related liver cancer in Han Chinese population. The polymorphisms of COX-2 -765 G/C was detected by polymerase chain reaction based restriction fragment length polymorphism (PCR-RFLP) in 300 patients with hepatitis B, 300 patients with cirrhosis, 300 patients with primary liver carcinoma and 300 health controls. The COX-2 -765 G/C genotypes were GG, GC and CC. There frequencies in the hepatitis B patients were 80.33, 17.67 and 2.00%; in the cirrhosis patients were 77.67, 18.00 and 4.33%; in the patients with primary liver carcinoma were 65.67, 28.33 and 6.00% and in the heathy controls were 87.00, 12.33 and 0.67%, respectively, COX-2 -765 C allele carriers had an increased risk of hepatitis B-related liver cancer. COX-2 -765 C allele carriers having drinking history or family history of liver cancer had higher risk for HCC. COX-2 -765 C allele genotype, drinking history and family history of liver cancer may increase the susceptibility to hepatitis B-related liver cancer in Gansu province, China.