In this work, we report our preliminary results for the presence of the vacancy, as well as for the boron and nitrogen impurities in non-passivated [001] silicon nanowires. The results show that defects and dopants tend to segregate to the nanowire surfaces, as observed for passivated [110] ones, but at the (-2) charge state, due to the metallic character of the [001] nanowire. The vacancies are stable at the facets, while the impurities stay preferentially at the interstitial site, making bridges with the lateral surface Si atoms, below to this surface. As a consequence, the surface -states located at the facets are filled and a small bandgap appears in the calculated defect band structures.