The role of phosphatases in cancer is an ignored research field, mostly based on the dogma that phosphatases function as tumor suppressor genes. However, in our opinion dephosphorylation events by phosphatases can also enhance signaling in cancer. The current research was therefore focused on elucidating the role of several phosphatases in cancer, concentrating on phosphatases which have the potential to act as oncogenes rather than tumor suppressor genes, and which can have clinical implications as biomarker or future treatment target. More specifically, we investigated the role of the Low Molecular Weight protein tyrosine phosphatase (LMWPTP) in colorectal and prostate cancer, and studied the role of the protein tyrosine phosphatase 1B (PTP1B) and lipid phosphatase SH2 domain containing inositol 5-phosphatase 2 (SHIP2) in colorectal cancer.