Abstract: The present invention relates to a process for the preparation of a gadolinium chelate compound of formula (I) or its stereoisomers, tautomers, N-oxides, hydrates, solvates, or salts thereof, or mixtures of same. Further, the present invention relates to crystalline forms of the gadolinium chelate of formula (I), to a process for the preparation of said crystalline forms as well as to intermediate compounds in the synthesis of the gadolinium chelate compound of formula (I) and/or its crystalline forms as well as their stereoisomers, tautomers, N-oxides, hydrates, solvates, or salts thereof, or mixtures of same.