We present the results of a systematic isochronal annealing investigation of vacancy-related defects in electron-irradiated n-type 6H-SiC:N. A series of 10 samples cut from a commercial wafer and annealed up to 1200 degreesC after electron-irradiation (1.5x10(18)cm(-3)) was characterized with Photoluminescence (PL), Magnetic Circular Dichroism of the Absorption (MCDA) and conventional Electron Paramagnetic Resonance (EPR). Apart from less stable triplet-related defects which vanished between 150 degreesC and 300 degreesC, the thermal behavior of three radiation-induced defects was studied: the silicon vacancy (V-Si), the carbon-antisite-carbon-vacancy pair (C-Si-V-C) and the D1 center. Their annealing behavior showed that the destruction of the isolated V-Si between 750 degreesC and 900 degreesC is followed by the formation of thermally more stable C-Si-V-C pairs, a result that has been theoretically predicted recently. By further heating the samples the C-Si-V-C pairs are annealed out between 900 degreesC and 1050 degreesC and were followed by an increase in the D1 center concentration.