Most patients with pancreatic ductal adenocarcinoma (PDAC) have a limited lifespan, because approximately half are initially diagnosed with distant organ metastatic disease. The most common site of metastasis is the liver, followed by the peritoneum, lungs and pleura, bones and adrenal glands. Recently, FOLFIRINOX or GnP provided clinical response rates of 30%-40%, and incidence or conversion surgery has been increasing, even in patients with metastatic PDAC. Some studies have shown that conversion surgery after a favorable response to anti-cancer treatment even in patients with metastatic PDAC might provide a potential survival benefit. Considering the relationship between surgical indication or resectability and MST, strict criteria, such as disappearance of metastasis on imaging studies and/or staging laparoscopy (Anatomical), decreases in tumor markers (Biological), and surgically-fit (Conditional) was associated with low resectability ranging from 4.5% to 8.7% but long MST ranging from 39 to 56 months from the initial treatment. We have implemented conversion surgery in the selected patients with initially liver metastasis or peritoneal dissemination who had favorable response to anti-cancer treatment for a certain period according to ABC criteria. In this lecture, our own clinical data will be presented, and optima indication and timing of conversion surgery in patients with metastatic disease will be discussed.