The structural and bonding properties have been predicted for AsO2 and AsS2 species in doublet state using density functional theory (DFT) and the second-order Moller-Plesset (MP2) method with 6-311 +G* basis set. The geometrical optimizations and the harmonic vibrational frequency analysis are performed using DFT methods. The relevant state-state energy separations are also determined using CCSD(T) and QCISD(T) methods. The results indicate that each species possesses a B-2(2) ground state. The AsO2((2)A(2)) should be classified as superoxide and the AsS2((2)A(2)) should be classified as supersulfide, but their ground states should be classified as dioxide and disulfide, respectively. (C) 2004 Elsevier B.V. All rights reserved.