Treatment of cadmium(II) thio- and selenocyanate with pyridazine leads to the formation of new cadmium(II)thiocyanato and selenocyanato coordination compounds [Cd(NCS)2(pyridazine)4] (1A), [Cd(NCSe)2(pyridazine)3]n (2A), [Cd(NCS)2(pyridazine)2]n (1B), [Cd(NCSe)2(pyridazine)2]n (2B) and [Cd(NCS)2(pyridazine)]n (1C) which were characterised by single-crystal X-ray diffraction. Investigations of the thermal degradation behaviour of 1A and 2A using simultaneous differential thermoanalysis and thermogravimetry as well as X-ray powder diffraction, IR- and Raman spectroscopy prove that on heating, the pyridazine-rich compounds 1A and 2A decompose in a stepwise manner leading in the first TG step to the formation of the pyridazine-deficient compounds [Cd(NCS)2(pyridazine)2]n (1B) and [Cd(NCSe)2(pyridazine)2]n (2B) as intermediates. While the selenocyanato compound decomposes on further heating, for the thiocyanato compound an additional TG step is observed, in which a pyridazine-deficient 1:1 compound of composition [Cd(NCS)2(pyridazine)]n (1C) is formed. The structures and thermal reactivity are discussed and compared with that of related transition metal thiocyanato and selenocyanato coordination compounds with pyridine and pyrazine as the coligand. More importantly, on the basis of these investigations, the hitherto unknown structures of the ligand-deficient paramagnetic counterparts were determined.