Deep optical identification of compact GB/GB2 radio sources from the sample of Machalski & Inoue (1990) are reported. The identification rate of the flat-spectrum sources is now as high as 98+/- 1%. Only in one case no optical counterpart was detected up to the limiting magnitude of R 22.5. Among all identified flat-spectrum sources in this sample 83% are QSOs or other stellar objects. Comparing the R-mag distribution for compact sources of different radio spectral index, and different radio luminosity, we found that this distribution and identification rate for compact sources, although dependent on the magnitude limit and radio spectral index, are almost independent on the type of optical object and its radio luminosity. This implies that the optical luminosity of those sources is in general unrelated to their radio luminosity.