Heparinoid derivatives comprising a chelating agent which is covalently bonded to the heparinoid, and a paramagnetic metal cation from the series of transition metals Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Ru or of the lanthanides, are suitable for producing medicaments both for therapy and for diagnostic purposes, for localizing the dose employed, and for monitoring the result of treatment of disorders such as thrombosis and osteoarthrosis.