smooth muscles are found in inner organs (eg: walls of blood vessels, urinary bladder, eye, skin etc) while cardiac muscles are found only in the heart
cardiac muscles are striated, but smooth muscles are non-striated
a cardiac muscle cell has one or more nuclei, but smooth muscle cells are single nucleated
cardiac muscle cells are often branched, but smooth cells are non-branched
smooth muscle cells are fusiform-shaped(spindle like shape), but cardiac muscle cells are long and cylindrical