In recent years the the set of diagnostic tools in colorectal cancers has been extended by the assessment ofthe KRAS gene status. Currently it is a necessary step in order to qualify patients for the targeted therapy. The results ofthe analysis of several studies revealed a high rate of compliance of the KRAS gene mutational status in primary and metastatictumors. In this paper we present a rare case of incompatibility of the KRAS mutations in the primary tumor located inthe colon and metastatic changes in the liver.