Colorectal cancer is the first cause of cancer in occidental countries if we consider both male and females tumours. In Spain, 26,000 new cases are diagnosed every year. The possibilities of cure are higher if the tumour is diagnosed early. One of the most important risk factors for colorectal cancer is inheritance. Some hereditary syndromes, such as familial adenomatous polyposis (FAP), increase the risk by almost 100% and at a young age. Other more prevalent syndromes, such Lynch syndrome, increase the risk 10-12 times more than in the general population. This article aims at summarising the most important aspects in hereditary colorectal cancer and to be a useful tool to oncologists who work with these patients and their families.