β-Hairpin peptidomimetics of the general formula cyclo(-Tyr1-His2-Xaa3-Cys4-Ser5-Xaa6-DPro7-Xaa8-Arg9-Tyr10-Cys11-Tyr12-Xaa13-Xaa14-Xaa15-Pro16-), disulfide bond between Cys4 and Cys11, and pharmaceutically acceptable salts thereof, with Xaa3, Xaa6, Xaa8, Xaa13, Xaa14 and Xaa15 being amino acid residues of certain types which are defined in the description and the claims, have favorable pharmacological properties and can be used for preventing HIV infections in healthy individuals or for slowing and halting viral progression in infected patients; or where cancer is mediated or resulting from CXCR4 receptor activity; or where immunological diseases are mediated or resulting from CXCR4 receptor activity; or for treating immunosuppression; or during apheresis collections of peripheral blood stem cells and/or as agents to induce mobilization of stem cells to regulate tissue repair.These peptidomimetics can be manufactured by a process which is based on a mixed solid- and solution phase synthetic strategy.