The aim of this study was to compare and externally validate risk scores developed to predict incident colorectal cancer (CRC) that include common genetic variants (single nucleotide polymorphisms, SNPs), with or without established lifestyle/environmental (questionnairebased/classical/phenotypic) risk factors. We externally validated 23 risk models from a previous systematic review in 443,888 participants aged 37-73 from the UK Biobank cohort who had 6 year prospective follow-up, no prior history of CRC and data for incidence of CRC through linkage to national cancer registries. There were 2,679 (0.6%) cases of incident CRC. We assessed model discrimination using the Area Under the Curve (AUC) and relative risk calibration. The AUC of models including only SNPs increased with the number of included SNPs and was similar in men and women: the model by Huyghe with 120 SNPs had the highest AUC of 0.62(95%CI 0.59-0.64) in women and 0.64(95%CI 0.61-0.66) in men.Adding phenotypic risk factors without age improved discrimination in men but not in women. Adding phenotypic risk factors and age increased discrimination in all cases (p<0.05), with the best performing models including SNPs, phenotypic risk factors and age having AUCs between 0.64-0.67 in women and 0.67-0.71 in men. Relative risk calibration varied substantially across the models. Among middle-aged people in the UK, existing polygenic risk scores discriminate moderately well between those who do and do not develop colorectal cancer over six years. Consideration should be given to exploring the feasibility of incorporating genetic and lifestyle/environmental information in any future stratified CRC screening program.