Pharmacogenomics is a very useful tool in current era of medical advancement as it contributes to individual profiling of each person suffering from a disease which can be lethal and requiring doses of medication unique to them. This is called individualisation of medication. But to find this unique dosage we have to first find the genes affecting the pathogenesis of that particular disease. Same is the case with Colorectal cancer (CRC) as we will study in this review. CRC treatment have been affected by various mutation in the RAF and RAS genes which are responsible. Different mutations lead to different level of sensitivity to drugs. The drugs used in colorectal cancer treatments are studied for the various aspects through which level of efficacy can be studied (mechanism of action, pharmacokinetics, toxicity) and through them we came to know about the genes which can be the cause of different genes and the different mutations in those genes which may be the reason for the different level of sensitivity to the drugs for each individual.