We have performed zero-field [mu ]SR measurements on high-quality single-crystalline samples of YRu 2 Si 2 , CeRu 2 Si 2 and Ce(Ru 0 . 8 5 Rh 0 . 1 5 ) 2 Si 2 from 2 K to 300 K. We got information on the diffusion and stopping site of muons in the ThCr 2 Si 2 structure from measurements on the non-magnetic reference compound YRu 2 Si 2 . The development of magnetic correlation of the Ce 4f moment was observed below 100 K on CeRu 2 Si 2 . Furthermore, the property of the antiferromagnetic ordering state of Ce(Ru 0 . 8 5 Rh 0 . 1 5 ) 2 Si 2 is discussed.