Genome-wide association studies (GWAS) have identified many genetic risk variants for cancers. The utility of these variants in assessing risk of esophageal, gastric and endometrial cancers, as well as melanoma, glioma, diffuse large B-cell lymphoma, follicular lymphoma, chronic lymphoid leukemia and multiple myeloma, has not been adequately investigated. We constructed a site-specific polygenic risk score (PRS) for each of these nine cancers using their GWAS-identified risk variants. Using data from 400 807 participants of European descent in the UK Biobank, a population-based cohort study, we estimated the hazard ratios of each cancer associated with its PRS using Cox proportional hazard models. During a median follow-up of 5.8 years, 3905 incident cases of these nine cancers were identified in the cohort. The area under the receiver operating characteristic curve ranged from 0.53 to 0.69 for these cancers. Except for esophageal cancer, significant dose-response associations were observed between PRS and cancer risk. Compared to individuals in the middle quintile (40%-60%) at an average risk, those among the highest 5% of the PRS had a twofold elevated risk of melanoma, glioma, follicular lymphoma or multiple myeloma, and a fourfold elevated risk of chronic lymphoid leukemia. Using PRS, 63.0% of the participants could be classified as having an over twofold elevated risk for at least one cancer. The PRS derived using risk variants identified to date by GWAS showed the potential in identifying individuals at a significantly elevated risk of cancer for prevention.