Owing to questions that still persist regarding the length of the OH and central OO bond, and large-amplitude torsional motion of trans hydridotrioxygen HOOO, a weakly bound complex between OH and O-2, new O-18 isotopic measurements of HOOO and DOOO were undertaken using Fourier transform microwave and microwave-millimeter-wave double resonance techniques. Rotational lines from three new O-18 species of DOOO ((DOOO)-O-18, (DOOO)-O-18-O-18, and (DOOO)-O-18-O-18-O-18) were detected, along with the two singly substituted O-18 isotopic species of HOOO ((HOOO)-O-18 and (HOOO)-O-18) that were not measured in the previous isotopic investigation. From a least-squares fit, spectroscopic constants, including the three rotational constants, were precisely determined for all five species. The inertial defect of DOOO and its O-18 species is uniformly negative: of order -0.04 amu 2, regardless of the number or location of the O-18 atoms, in contrast to that found for HOOO or its O-18 isotopic species. A reanalysis of the molecular structure was performed using either normal HOOO and its four singly substituted isotopic species, the new DOOO data, or all the isotopic species (10 in total). The differences between the purely experimental (r(0)) structures are generally quite small, of order +/- 0.01 for the bond lengths and +/- 1 degrees for the bond angle. The length of the OH bond remains unrealistically short compared to free OH, and the central OO bond length is consistently very close to 1.68 angstrom. On the basis of the effective OH bond length derived from the experimental structure, the average displacement of the large amplitude torsional motion from planarity is estimated to be similar to 22 degrees.