Over the past decade, increasing evidence suggested that stem cells play a crucial role not only in the generation of complex multicellular organisms, but also in the development and progression of malignant diseases. For the most abundant tumours, it has been shown that they contain a subset of distinct cancer cells that is exclusively responsible for tumour initiation and propagation These cells are termed cancer stem cells or tumour-initiating cells and they are also highly resistant to chemotherapeutic agents. Because CSC are preferentially endowed with the self-renewal capacity, it has further been hypothesized that they are also exclusively responsible for metastasis. Indeed, we were able to show that pancreatic cancer stem cells contain a subpopulation of migrating cancer stem cells characterized by CXCR4 co-expression. Only these cells are capable of evading the primary tumour and metastasizing. Laboratories around the world are now aiming to further characterize these cells to eventually identify novel treatment modalities to fight cancer. Thus, cancer stem cells are promising new targets to counteract the growth-promoting and metastatic potential of solid tumours.