We present a refined study of some isomers of the covalently bound O-8 molecule at the MP2 and CCSD levels with sequences of correlation-consistent basis sets. The previously known symmetric D-4d crown structure is 28 kcal/mol more stable than the structure by Forte et al. (Phys. Lett. A 377 (2013) 801), which is a second order transition state leading to 4O(2)((3)Sigma(-)(g)) and to another lower-lying unstable cyclic structure. The O-8 symmetric crown lies 104 kcal/mol above the 44O(2)((3)Sigma(-)(g)) fragments and has 1.40 angstrom O-O bonds, which are shorter than those of the O-4 and O-6 cyclic species at the MP2/CBS level. (C) 2013 Elsevier B.V. All rights reserved.