Colorectal cancer is one of the most common neoplasms worldwide. It is still characterized by high mortality and causes ¼ of deaths due to neoplasms. Synchronous cancer is defined as presence of more than one cancer focus (not metastatic) in a patient at the same time. Prevalence of synchronous cancer amounts to 1.1–8.1% of all colorectal carcinomas. More often it affects elderly people and men. Risk factors include inflammatory bowel diseases, hereditary non-polyposis colorectal cancer and familial adenomatous polyposis. Molecular mechanisms underlying the synchronous lesions are: microsatellite instability (MSI), P53 and KRAS mutations as well as glutathione S transferase mutations (GST). In this article, we present a case of a 76-year-old woman with synchronous colorectal cancer in the form of tumors of the sigmoid colon and the ascending colon with metastasis in the liver.