Our previous studies revealed three different types of N-O bonding: the 'normal' covalent bond, characterized by the bonding V(N,O) basin, the protocovalent bond, characterized by two non-bonding basins, V(N), V(O), and a bond characterized by a non-bonding basin, V(N). The results suggest that the formally single N-O bond, containing no ELF-basins, is possible. Our study confirms its existence in the (CF3)(2)NO-NO molecule. (C) 2011 Elsevier B. V. All rights reserved.