We present a detailed analysis of the spatial distribution of the stellar populations in the Galactic globular cluster omega Centauri. Taking advantage of the large photometric catalog published by Pancino et al. (2000), we confirm that metal-rich populations have a spatial distribution which is significantly different from the metal-poor dominant population. In particular: (i) the different sub-populations have different centroids and (ii) the metal-poor population is elongated along the E-W direction, while the metal-rich populations are oriented along the orthogonal direction, i.e., N-S. The evidence presented here can partially explain the weird spatial metallicity segregation found by Jurcsik (1998), and further supports the hyphothesis that different sub-populations in omega Centauri might have had different origins. Comment: 9 pages, 5 figures, accepted for publication in the MNRAS