The infrared spectrum of the weakly-bound trimer CO - (CO2)(2) is observed in the carbon monoxide CO stretch region. Both (CO)-C-12-O-16 - ((CO2)-C-12-O-16)(2) and (CO)-C-12-O-16 - ((CO2)-C-12-O-18)(2) isotopologues are studied. The trimer band which is composed uniquely of b-type transitions and with missing levels establishes the trimer structure as that of a CO2 dimer plus a CO monomer aligned along the dimer C-2 symmetry axis. The dimer to monomer center of mass separation is 3.55 angstrom, and the structural parameters within the CO2 dimer subunit are about 3.45 angstrom and 58 degrees. It is not certain if the (CO2)(2) remains planar within the trimer. (C) 2017 Elsevier B.V. All rights reserved.