Abstract. Effects of laser shock peening, water jet cavitation peening, water jet shot peening, and ultrasonic impact treatment on surface roughness, hardness, and residual stress of AISI 304 stainless steel were studied. Owing to new surface relief formation, the Ra roughness parameters became lower after ultrasonic and shot peening than those after laser and cavitation peening. The ultrasonic processing led to the highest surface hardness among the studied peening treatments. The optimum regimes were determined by accounting for the minimum magnitudes of surface roughness and maximum magnitudes of the surface hardness and residual stresses. In comparison with the initial state, these regimes result in the HRC surface hardness increase (LSP2 ~30.7%, WjCP2 ~38.4%, WjSP2 ~69.6%, UIT4 ~73.2%) and in the Ra roughness parameter reduction (LSP2 ~5.5%, WjCP2 ~7.8%, WjSP2 ~38.2%, UIT4 ~91.1%) inducing the compressive residual stress (LSP2 –470 MPa, WjCP2 –377 MPa, WjSP2 –519 MPa, UIT4 –693 MPa).