Colorectal cancer represents a major health problem in the western world. A lot of drugs have been employed in treatment of this disease, but only few data are available about predictive factors for response to anticancer treatments in colorectal cancer. Aim of this paper is to review the main data about this investigation field. Using a Medline database search (1966-2003) we reviewed all the relevant papers that investigate clinical and molecular predictors for response to the main drugs used in the treatment of colorectal cancer patients, both in adjuvant and in advanced setting. Moreover we comprehensively reviewed all the data published in abstract form during the most significant international meetings. Our review put in evidence the most important predictive factors for response in colorectal cancer patients treated with anticancer chemotherapy both in adjuvant and in advanced setting. The predictive factors are clustered on the basis of the different anticancer drugs. The results of this review provide the rationale basis for personalizing anticancer treatment in colorectal cancer patients by molecular and clinical features, aiming to improve response rate and reduce toxicities.