Provided are MUC 18 targeting peptides which may be used, e.g., to therapeutically target B-I lymphocytes to reduce the influence of these cells on the metastatic potential of melanoma cells and/or to target cancerous cells, including certain melanoma and leukemia cells. MUC 18 targeting peptides may be comprised in fusion constructs, imaging constructs, and/or therapeutic constructs such as fusion constructs which may be used for diagnosing or treating a cancer.