In this paper we report on the performances and on the reliability study of AlGaN/GaN HEMTs grown onto misoriented 4H-SiC substrate, 8° off-axis along the [11-20] direction. The substrate’s misorientation have produced defects preferentially oriented along the cut direction, limiting the carrier transport along the orthogonal direction. As a consequence, it has been observed a strong anisotropy of the electrical performances between devices processed along the two directions. Despite this different electrical behaviour, the paper will show that device robustness appears not to be influenced by the big defects presence.