Commercial geese breeding in Poland is based on two strains ofWhite Italian geese (W11 and 33). The crossbreeds W33 ( paternal line ) and W11 ( maternal line ) are distributed in Poland under the commercial brand of White Ko?uda? goose. However, there are several breeds which are covered by the animal genetic resources conservation program and kept as conservative flocks. These breeds proved invaluable to commercial geese breeding to stabilize body weight, improve muscling and decrease the amount of fat in the carcass of the crossbreeds. Therefore, this study analyzed the reciprocal crossbreeds of White Ko?uda? geese with the individuals from conservative flocks. DNA polymorphism (RAPD-PCR) of the crossbreeds as well as the phenotypic effect of crossbreeding was evaluated. PCR amplification of five RAPD markers resulted in obtaining 14.25 band/crossbreed group. The genetic similarity of the crossbreeds expressed as band sharing frequency (BS) ranged from 0.44 to 0.97. The direction of crossing of theW33 goose with one of the individuals from the conservative flock strongly affected the genetic similarity estimates. The body weight in the 17th or 24th week of life and the percentage of leg muscle weight in the 24th week of life differed significantly depending on the crossbreed genotype. A similar relationship was demonstrated for egg fertilization and number of nestlings per goose. As the lines were differentiated only by origin of the Z chromosome, the background of the differences in genetic polymorphism and the phenotypic records is hypothesized as (i) the linkage of some production traits with sex chromosomes; (ii) the impact of selection on W33 individuals resulting in lower performance of geese with a W33-derived Z chromosome; (iii) genetic imprinting displayed as the effect of eithermaternal or paternal origin of the Z chromosome.