We have investigated the morphologic and electronic properties of self-organized nanosized Cr islands grown on atomically flat Au(111) surfaces by means of low-temperature scanning tunneling microscopy and spectroscopy under ultra-high vacuum conditions. We observe the existence of an electronic surface state on the Cr islands, which manifests itself through the formation of standing wave patterns within the interior of the atomically flat islands that gain in complexity for increasing bias voltages. The patterns are only weakly observable when compared to similar standing waves formed within self-organized Co islands on Au(111). This difference is attributed to the more irregular shape of the Cr islands. Furthermore, we have found that the presence of the Cr surface state is reflected by the appearance of a distinct electronic state in the -200 mV to -150 mV range, resembling to previous findings for self-organized Co islands on Au(111).