The invention relates to a cationic complex of technetium-99m with (a) at least one bidendate ligand X having the formula R1 R2 ZQZR3 R4 where each Z is phosphorus or arsenic, Q is a (CH2)n linking group where n is 2 to 8 or a 1,2-phenylene linking group, each of R1, R2, R3 and R4 is hydrogen, C1 to C5 alkyl or phenyl; and (b) at least one monodentate isonitrile ligand Y. The invention also relates to a radiopharmaceutical composition comprising said complex, to a kit for preparing said composition, and to the use of said composition for a radiodiagnostic examination.