The invention relates to tumour therapy. In one aspect, the present invention relates to conjugates of a toxin and a target-binding moiety, e.g. an antibody, which are useful in the treatment of cancer. In particular, the toxin is an amatoxin, and the target-binding moiety is preferably directed against tumour-associated antigens. In particular, the amatoxin is conjugated to the antibody by linker moieties. In particular the linker moieties are covalently bound to functional groups located in positions of the amatoxin proved as preferred positions for the attachment of linkers with respect to optimum antitumor activity. In a further aspect the invention relates to pharmaceutical compositions comprising such target-binding moiety toxin conjugates and to the use of such target-binding moiety toxin conjugates for the preparation of such pharmaceutical compositions. The target-binding moiety toxin conjugates and pharmaceutical compositions of the invention are useful for the treatment of cancer.