A detailed cross-sectional HREM (high-resolution electron microscopy) investigation of the microstructure of porous layer obtained by electrochemical etching of 6H-SiC bulk substrate is presented. High-resolution electron microscopy reveals the existence of a disordered layer at the interface between crystalline SiC and the pores. EDX (energy-dispersive x-ray spectroscopy) spectra of this layer proved conclusively that it is not amorphous SiC (50%Si + 50%C) but a carbon rich phase. In the crystalline area of pores stacking faults on (0001) planes are produced. These give rise to streaks connecting the transmitted spot with (0002) reflections in the corresponding selected area diffraction patterns. The mechanism of electrochemical etching is discussed.