Agents used in medical tumor therapies can cause peculiar cutaneous side effects. In particular the newly developed targeted therapies are associated with specific cutaneous side effects, such as a papulopustular exanthems associated with EGFR inhibitors and epithelial skin cancers associated with inhibitors of mutated BRAF. In this review the clinical pictures as well as pathogenetic and therapeutic aspects of the hand-foot-syndrome, papulopustular exanthems, epithelial skin cancers, paronychia and changes of hair and nails as side effects of medical tumor therapies are summarized. Knowledge of these side effects is important to avoid interruption or termination of the tumor therapy, in particular since some of the cutaneous reactions have been shown to correlate with the therapeutic benefit of the tumor therapy.