Compounds of formula (I) RA—CO—N(R2)—(CR12)n—N(R5)—RB and salts or optical active isomers thereof, wherein each R1 independently are the same or different and denotes a hydrogen atom, a hydroxyl group, a C1 to C4 straight of branched alkyl group or a C1 to C4 straight of branched oxyalkyl group R2 denotes a hydrogen atom or a C1 to C4 straight of branched alkyl group R5 independently are the same or different and denotes a acyl moiety RA and RB independently are the same or different and denote a triiodinated phenyl group, preferably a 2,4,6-triiodinated phenyl group further substituted by two groups R3 in the 3 and 5 positions wherein each R3 are the same or different and denote a hydrogen atom or a non-ionic hydrophilic moiety, provided that at least one R3 group in the compound of formula (I) is a hydrophilic moiety and n denotes a positive integer of 1 to 6. The invention also relates to the use of such diagnostic compositions as contrast agents in diagnostic imaging and in particular in X-ray imaging, and to contrast media containing such compounds.
