1. Background: state of research/ scientific arguementation/ leading question In the last 20 years, the surgery of colorectal liver metastases has developed a lot (8,9,10,11). In centers even complex surgeries can be done with a mortality of 0,1% and with a morbidity of 15%. Today, neither the number, nor the localisation of metastases or an extrahepatic tumour growth is decisive for a resection, but the fact, if there is a possibilty for a complete tumor excision (12). Especially because of the further developement of neoadjuvant (13) and adjuvant (14) chemotherapeutics on the one hand and the technical developement (portal embolisation (15), two-time resection (16), virtual operation planning (4), navigated surgery (17)) on the other hand enlarged the number of patients becoming resectable secondarily.