  Motivated by the recent discovery of noncentrosymmetric superconductors, such
as $CePt_{3}Si$, $CeRhSi_{3}$ and $CeIrSi_{3}$, we investigate theoretically
the impurity resonance states with coexisting $s$- and p-wave pairing
symmetries. Due to the nodal structure of the gap function, we find single
nonmagnetic impurity-induced resonances appearing in the local density of state
(LDOS). In particular, we analyze the evolution of the local density of states
for coexisting isotropic s-wave and p-wave superconducting states and compare
with that of anisotropic s-wave and p-wave symmetries of the superconducting
gap. Our results show that the scanning tunneling microscopy can shed light on
the particular structure of the superconducting gap in non-centrosymmetric
superconductors.
