The invention provides ligands of ganglioside GD2, including peptide ligands such as GGITNYNSALM; YCGGITNYNSACY; YCITNYNSCY; YCGGITNYNCY; YCTNYGVHCY; YCTNYGVCY; GGIANYNTS; YCGGIANYNCY; YCGGIANYNTSCY; and, YCIANYNTCY. GD2 ligands of the invention may for example be used to treat or diagnose diseases such as cancers in which cells express GD2, including neuroblastomas.