Nitrogen implants were performed in Si wafers of variable purity, i.e., epitaxial layers, float zone, and Czochralski silicon (CZ-Si). The diffusion behavior of nitrogen reported by Hockett in Appl. Phys. Lett., 54, 1793 (1989), where nitrogen diffuses for several micrometers at temperatures as low as 750degreesC and the profiles assume a "double-peak'' structure, is peculiar of CZ-Si. In contrast, in pure epitaxial-Si, nitrogen is immobile at low temperature but, at a higher temperature (850degreesC), the broadening of the nitrogen profile never assumes the shape observed in CZ-Si. Our results suggest that oxygen determines the shape of the nitrogen diffusion profiles. (C) 2004 The Electrochemical Society.